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Managing Managers

2024-03-11T00:00:00Z

Changing Role

Overseeing a Team Lead Manager (TLM) or Engineering Manager (EM) means being indirectly responsible for the group of Individual contributors (ICs) this TLM or EM is managing. Moving from an individual team manager, this shifts the focus from managing the direct outputs of the team to the broader outcomes of multiple teams.

Avoiding micromanagement, it will be important to be supporting the manager in delivering their results, watching for blind spots, gaps in project plans, and keeping team development aligned with a larger perspective. Asking questions, fostering learning opportunities, and focussing on coaching rather than solving problems directly.

The manager of managers' role is to ensure clear communication and alignment within the EM/PM partnership to allow the team to focus on efficiency and delivery, while taking ownership of handling external roadblocks.

Larger Leverage

‘Leverage’ is the ability to deploy resources towards an outcome, whilst reducing wastage.

A team focused on the right outcomes produces positive results. Applying pressure or leverage on a team which is misaligned, or applying this at the wrong time, can undermine the performance of the team, leading to wasted effort and costing the opportunity to work on other activities.

A manager of managers will have a broader scope, more responsibility, and more resources. All of this means that more pressure or leverage can be applied, with much larger impact – for better or for worse.

This double-edged sword of leverage means decisions can be more complicated and carry larger amounts of risk. Mitigating this risk by keeping close to the development teams, seeking feedback from customers and ICs, and staying close to partners across the business.

Outcomes over Output

Emphasis of results as the outcomes of the work performed by the team, not the effort or output. What are the tangible outcomes driven by the teams' work, and how are these driving the business forward? The alignment of teams and the work they undertake is only measured by the changes in these business outcomes.

The details of how the outcomes are produced is related to the output. As an engineering leader, it is your responsibility to ensure that the teams' efforts and outputs are aligned to achieve the best outcomes. And with this shift, is also a change in how the teams' output is monitored.

As you move away from the day-to-day detail of the teams' progress and output, you have less direct information about smaller scale challenges and decisions. When to cut corners, cut scope, or how much to invest in exploring a particular opportunity.

Managing indirectly will require concerted effort to maintain communication channels to keep visibility into the progress, challenges, and outcomes. This includes participating in demos and architecture reviews, monitoring dashboards and sprint reports, reviewing release notes, and holding 1:1s.

Further

Some topics to explore for managers of managers:

Shifting to indirect management
Mentoring managers
Managing relationships and resolving conflicts
Setting performance expectations and measuring results
Effective leadership with organisation politics
Continual growth as a leader

Thanks for the Feedback

2023-12-14T00:00:00Z

TLDR summary of key points

There are several types of feedback: Appreciation, Coaching, Evaluation - understanding their distinct purposes.
Each individual has preferences for receiving feedback
Managing and depersonalizing emotional responses for more productive conversations.
Viewing feedback as an opportunity for learning and improvement.
Actionable strategies for giving and receiving feedback effectively.

Thanks for the Feedback is a dynamic guide unravelling the intricacies of feedback, offering tools for growth, understanding, and communication mastery.

In Thanks for the Feedback, authors Douglas Stone and Sheila Heen dive into the often challenging realm of feedback, offering insight on how to receive and make the most of feedback in various aspects of life. The book is a practical guide for individuals seeking to navigate the tricky terrain of constructive criticism and use it as a catalyst for personal and professional development.

One of the strengths of the book lies in the anecdotes and real-life examples. From workplace dynamics to personal relationships, the authors illustrate how feedback is an integral part of our lives, shaping our growth and relationships.

The authors assert that feedback is a two-way street and that understanding the dual role of the receiver and the giver is crucial for effective communication. They identify three types of feedback - appreciation, coaching, and evaluation - each serving a distinct purpose. The book emphasizes that recognizing the type of feedback being given is essential for interpreting and responding appropriately. Delving into the complexities of emotional triggers, shedding light on why feedback can often elicit strong emotional responses. By acknowledging and managing these triggers, readers are guided on a path toward more constructive conversations. The book offers practical tools for depersonalizing feedback, making it easier to absorb and act upon.

Thanks for the Feedback also emphasizes the importance of a growth mindset. Readers are encouraged to view feedback as an opportunity for learning and improvement rather than as a critique of their abilities. By reframing feedback in this light, individuals can transform setbacks into stepping stones for personal and professional development.

In the final chapters, the authors provide actionable strategies for both giving and receiving feedback effectively. From the art of asking for feedback to providing it in a way that promotes growth, the book equips readers with the tools needed to navigate the feedback loop with confidence.

I can recommend Thanks for the Feedback for anyone looking to enhance their communication skills and cultivate a growth mindset. Whether you're a leader seeking to build a positive feedback culture in your team or an individual striving for personal growth, this book offers a roadmap for navigating the world of feedback with confidence, grace and resilience.

Phone Use Contract Template

2023-11-25T00:00:00Z

As parents, we are looking for ways to empower our children to use technology in positive ways and understand how to best use the devices, whilst also understanding the cost, responsibilities, and repercussions of misuse.
This template is adapted from the sample on VeryWellFamily.com.

Phone Use Contract

This is a contract between the Child and the Parents and establishes the Conditions, Provisions, and Consequences regarding responsible phone use.

Conditions of responsible phone use

The Child will abide by the following conditions of responsible phone use at all times.

I will share my phone's password with my parents and they may use it to check my phone at any time.
I will not send threatening or mean texts to others.
I will not send embarrassing photos of my family or friends to others.
I will not use my phone's camera to take embarrassing photos of others.
I will not use my phone to bully another person.
I will not use my phone to buy or download anything without asking permission first.
I will not text or place phone calls after 9 p.m.
I will keep my phone charged at all times.
I will answer or respond promptly when my parents contact me.
I will not go over the plan's data usage. If I do, I understand that I may be responsible for paying any additional charges or that I may lose my phone privileges.
I understand that I am responsible for knowing where my phone is, and for keeping it in good condition.
I will obey the rules of etiquette regarding phones in public places. I will make sure my phone is turned off when I am in church, restaurants, or other quiet settings.
I will obey any rules my school has regarding phones, such as turning them off during class.
I will alert my parents if I receive suspicious or alarming phone calls or text messages.
I will alert my parents if I am being harassed by someone via my phone.

Provisions of a phone and service

We the Parents, commit to the following provisions regarding responsible phone use.

We will supply at no cost to the Child a basic phone that will make and receive phone calls and text messages.
We will provision at no cost to the Child a basic phone plan to allow a suitable number of phone calls and text messages.

Consequences for breach of Conditions

The following consequences will be applied if the conditions of responsible phone use are not adhered to by the Child.

I understand that having a phone is a privilege and that if I fail to adhere to this contract, my phone privilege may be revoked and the phone will be confiscated.
If needed, I will be required to pay for any phone repair or replacement costs and for any excess charges that I incur without permission from my parents.

I hereby agree to abide by these conditions of responsible phone use.

Signed
The Child:
The Parents:
Date:

Transformational Leadership in Software Engineering

2023-08-18T00:00:00Z

Transformational leadership is a leadership style that goes beyond traditional managerial roles. It involves leaders who encourage their team members to exceed their own expectations and achieve exceptional outcomes. This leadership style revolves around four key components:

Idealised Influence: Transformational leaders serve as role models, earning the respect and admiration of their team by embodying the values and behaviours they seek in their team members. In the context of software engineering, this could mean showcasing a passion for coding, a commitment to quality, and a willingness to collaborate and learn.
Inspirational Motivation: These leaders have the ability to inspire and motivate their teams by setting a compelling vision and creating a sense of purpose. They connect team members to the larger mission of the project, fostering enthusiasm and dedication to the work at hand.
Individualised Consideration: Transformational leaders pay close attention to the individual needs and aspirations of their team members. They provide personalised support, coaching, and mentoring, which can be particularly valuable in a cross-functional team where skill sets and personalities vary widely.
Intellectual Stimulation: These leaders encourage creativity and innovation by challenging their team members to think critically and explore new solutions. They promote an environment where team members feel safe to voice their ideas and take calculated risks.

Benefits of Transformational Leadership

When applied to cross-functional software engineering teams, transformational leadership offers several notable advantages. Transformational leaders foster a culture of open communication and collaboration. This is essential in cross-functional teams where individuals from different disciplines need to work seamlessly together.

By encouraging innovative thinking and providing a safe space for experimentation, transformational leaders stimulate creativity within the team. This can lead to the development of novel solutions and more efficient processes. With a focus on individualised consideration and intellectual stimulation, transformational leaders help team members reach their full potential. This, in turn, can lead to higher-quality software products.

In the dynamic realm of software engineering, change is constant. Transformational leaders prepare their teams to adapt by fostering a culture of continuous learning and resilience.

Challenges and Considerations

While transformational leadership has numerous benefits, it's not without its challenges. Balancing individual attention with project demands, ensuring consistency across a diverse team, and managing expectations are all potential hurdles that leaders need to navigate.

Transformational leadership has the potential to greatly benefit cross-functional software engineering teams. By inspiring, motivating, and empowering team members, leaders can cultivate a culture of collaboration, innovation, and excellence. In a field where adaptability and creativity are paramount, embracing transformational leadership principles can pave the way for successful software projects and the growth of both individuals and the team as a whole.

Impact to Advancement

2023-08-16T00:00:00Z

As a follow-up to the previous article on preparing for performance reviews as a software engineer, let's delve deeper into how you can not only navigate the review process but also amplify your impact within your organisation. In this article, we will explore advanced strategies for elevating your performance review experience and solidifying your path towards professional growth and advancement.

1. Elevating Your Contributions

While identifying key performance criteria and aligning your efforts is crucial, consider taking it a step further by actively seeking opportunities to contribute beyond your defined scope. Proactively engage in projects or initiatives that are not only relevant to your current role but also align with the company's broader goals. By demonstrating your ability to go above and beyond, you showcase your dedication and commitment to the organisation's success.

For instance, if your key performance area is "event-driven serverless architecture," explore ways to propose innovative solutions that optimise existing processes or enhance system performance. Your ability to initiate positive change will set you apart and strengthen your position during performance evaluations.

2. Mastering Collaboration

Collaboration is a cornerstone of successful engineering teams. In addition to your technical prowess, your ability to collaborate across departments and teams can significantly impact your performance review. Actively seek out opportunities to participate in cross-functional projects, mentor colleagues, or share your expertise in knowledge-sharing sessions. These actions not only foster teamwork but also spotlight your leadership skills and commitment to collective growth.

By documenting instances where you facilitated collaboration, resolved conflicts, or mentored peers, you create a compelling narrative of your holistic contributions, positioning yourself as an indispensable asset to the team.

3. Enriching Skill Diversification

While emphasising key areas is essential, don't underestimate the value of cultivating a diverse skill set. As the tech landscape evolves, software engineers who possess a wide range of proficiencies are highly sought after. Pursue opportunities to learn new technologies, programming languages, or methodologies that align with the organisation's evolving needs.

For instance, if your organisation is transitioning to a new tech stack, proactively engage in upskilling initiatives to ensure a seamless transition. Your willingness to embrace change and expand your knowledge base not only prepares you for future challenges but also positions you as a versatile contributor who can adapt to dynamic circumstances.

4. Crafting Impactful Documentation

While documenting your achievements is emphasised in the initial article, consider elevating your documentation strategy. Rather than solely recording outcomes, delve into the thought processes, challenges, and iterative improvements that led to your successes. This not only provides a comprehensive view of your contributions but also showcases your analytical thinking and problem-solving abilities.

Additionally, consider creating a portfolio that highlights key projects, the challenges you tackled, and the innovative solutions you devised. Visual aids, code snippets, and before-and-after comparisons can offer a vivid demonstration of your journey and accomplishments.

5. Seeking Mentorship

Advancing your career isn't just about personal achievements; it's also about fostering growth in others. Seek mentorship opportunities, not only from senior colleagues but also from your mentees. The act of mentoring not only strengthens your skills as a leader but also underscores your commitment to the development of your team and the organisation as a whole.

During performance reviews, showcasing the impact of your mentorship—whether through the growth of junior engineers, successful team projects, or knowledge-sharing initiatives—attests to your ability to contribute to a positive and thriving work environment.

Conclusion

In software engineering, performance reviews are not just about demonstrating your capabilities but also about showcasing your potential to drive meaningful change. By celebrating your contributions, mastering collaboration, enriching your skill set, crafting impactful documentation, and embracing mentorship, you create a comprehensive narrative of your value to the organisation.

Remember, the review process is not just an evaluation—it's an opportunity to redefine your role, amplify your impact, and shape your future within the company.

Preparing for Performance Reviews

2023-06-28T00:00:00Z

As a software engineer, performance reviews play a crucial role in assessing your professional growth and determining future opportunities within your organisation. To ensure a successful review process, it is essential to proactively identify key areas of focus, seek out opportunities to showcase your skills, and document your accomplishments.

Preparing for the review

Identify key performance criteria
Seek opportunities to work in the key areas
Document your impact in the key areas
Demonstrating your impact in each key area

Identify key performance criteria

Before entering the review process, it is important to set yourself up for success by first defining what a successful outcome means for you. Have a conversation with your manager about your desired next role and the type of work you are looking to do.

Examine the position description for the role at your current level and the position description for the role at your desired level to identify the different responsibilities, behaviours, and impacts required of the next role. These will become the key areas to focus on as you look to develop your skills and demonstrate them as you work towards your next performance review.

Some examples: "Demonstrates knowledge of event-driven serverless architecture", "Demonstrates ability to deliver cross-functional software projects", or "Provides mentoring for junior team members".

If your workplace uses KPIs or, preferrably, OKRs, use these key areas to help define goals that will track your progress. This will help you double-down on your documentation and provide even more evidence for your impact during the review process.

Seek opportunities to work in the key areas

Having identified the key areas required for your next role, take the opportunity to discuss with your manager any opportunities that may be available to work on projects that align with these development goals.

Actively seek out opportunities within your team to gain experience and expertise in these domains. Volunteer for projects or tasks that allow you to demonstrate your skills and contribute to the success of your team. Collaborating on cross-functional teams, taking the lead on challenging tasks, writing documentation, or participating in professional development programmes can also help you broaden your skill set and make an impact in the identified areas.

Example: Offering to pair with junior team members to demonstrate having an impact in a key area of "mentoring junior team members".

Document your impact in the key areas

While working on projects and assignments that are aligned with your key development areas, it is crucial to document your contributions and the impact they have had on the organisation. Keep a record of the tasks you have undertaken, the challenges you have overcome, and the outcomes you have achieved. This documentation will serve as evidence of your ability to deliver results and showcase your value to the company. Quantifiable metrics, such as improved efficiency, cost savings, or customer satisfaction ratings, can significantly strengthen your case during the performance review.

Example: Key Area: Project Leadership: Demonstrated project leadership by facilitating a delivery planning session and developing a roadmap including delivery milestones, dates, and dependencies. Documented this plan and communicated the decisions with the project stakeholders.

Setting aside time at the end of each week, month, or sprint to regularly check in and document your work will make it easy to keep this information up-to-date and comprehensive.

Demonstrating your impact in each key area of your next role

During your performance review, you will likely be evaluated based on the specific requirements and responsibilities of the role you have nominated for your promotion.

To effectively demonstrate your readiness for the additional responsibilities, you can present evidence that demonstrates how you have been working across the key areas and have been able to fulfil each of the requirements of the role, using one or more examples of recent work that showcase your capabilities.

Following this pattern for each of the requirements for your desired role, you will place yourself in the best position for the performance review.

By delivering work aligned with the key areas of your desired role, actively seeking opportunities to develop your skills, and documenting these achievements, you can effectively showcase your impact with the organisation as a software engineer and position yourself as the perfect example of a candidate for your desired role.

Building a Resilient Engineering Team

2023-06-23T00:00:00Z

In software engineering, stress and burnout are increasingly challenges that both individuals and teams face.

As a software engineering manager, it is essential to prioritise the well-being of your team members and create a resilient engineering team.

Working across several teams in the past few years, some effective strategies I have found for managing stress and burnout within a team have been to focus on career and development plans, be clear about communication expectations and time management, and manage delivery performance expectations with stakeholders.

Career Development Plans

One method I have found to support my team members and promote resilience is by implementing career development plans. These plans provide a framework to discuss growth and advancement opportunities. Knowing the areas team members are interested in can allow them to take on those challenges and engage in the work that brings them satisfaction. Engaging in regular conversations with your engineers helps you understand their aspirations, interests, and areas for development.

By investing in their professional growth, you demonstrate your commitment to their long-term success and well-being.

Managing Time and Communication Expectations

Setting time and communication expectations plays a key role in preventing stress and burnout. Encourage your team to prioritise their work effectively, set realistic expectations for deliverables, and communicate the requirements and expectations around response times. Helping them identify potential blocking issues, bottlenecks and discractions, can provide support in managing their workload. Regularly review project scope and delivery time lines and adjust them if necessary, to maintain a sustainable pace of work that allows for a healthy work-life balance. Fostering a culture of open communication where team members feel comfortable discussing challenges, seeking assistance, and expressing concerns will help identify any issues early and reduce the impact of last-minute changes.

Check in with the Team

Regularly checking in with your team members is crucial for understanding the state of their well-being and beginning to identify any individual or common potential stressors. Scheduling regular one-on-one meetings to discuss their workload, challenges, and overall satisfaction is my highest priority when working with a new team. Actively listening to their concerns with the aim of first understanding their position and desires, then seeking to provide the necessary support or resources. Being heard is important for team morale.

Building a resilient engineering team requires a proactive approach from software engineering managers. By implementing strategies such as career and development plans, setting time and communication expectations, and regularly checking in with the team, you can create an environment that promotes well-being, reduces the chance of burnout, and enhances team resilience. Prioritising work-life balance and fostering open communication will contribute to a healthier and more productive team, which will not only be more successful in the long run but also be more satisfied and engaged in their work.

Career Change to Software Engineering

2023-05-08T00:00:00Z

I was recently asked for some advice and for some feedback on a portfolio and thought I'd share some general advice here for presenting your portfolio and resume as you make the transition into a software engineering career.

If you're looking to make a career change into software engineering, you're in luck. Software engineering is one of the most in-demand professions, and the demand is expected to continue to grow in the coming years. However, competition for entry-level software engineering jobs can be tough, and that's why having a well-presented portfolio and resume can make all the difference.

Use your portfolio to highlight your problem solving skills

When it comes to your portfolio, your projects are the main event. It's important to focus on the challenges you faced and how you overcame them. Was it a particular skill, tool, technology, or architectural pattern? Make sure to highlight what you learned from each project. This will not only showcase your technical skills but also your ability to learn and adapt. Remember to present your projects in a clear and concise manner, with attention to detail and good documentation.

GitHub is a popular platform to showcase your work. Uploading your projects to GitHub can help potential employers easily review your code and see the work you've done. It's important to maintain good coding practices and to keep your repositories up to date. Be sure to include a link to your GitHub profile on your resume and portfolio so that potential employers can easily access and review your work.

Emphasise your transferable skills and tailor your resume for each opportunity

As a beginner in software engineering, it's essential to emphasize your soft skills. These include your ability to learn, determine project requirements, communicate effectively, and collaborate with others. These skills are just as important as technical skills when it comes to working in a team. Be sure to highlight how you have applied these skills in your past experiences, including any team projects or extracurricular activities.

While a standard resume is great, customizing your resume for each employer is even better. Take the time to review the job postings of the companies you're interested in and highlight where your skills align with their values and requirements. By doing so, you'll have a much higher chance of getting a call back. Make sure to tailor your resume to each job posting and emphasize the skills and experiences that are most relevant to the role.

Finally, don't be afraid to seek feedback from others. Reach out to software engineers in your network and ask them to review your portfolio and resume. Their feedback can help you identify areas for improvement and give you a better chance of landing your dream job. Consider joining online communities, such as LinkedIn or Reddit, where you can connect with other software engineers and receive valuable feedback on your work. Remember to take the feedback constructively and use it to improve your portfolio and resume.

Transitioning into software engineering can be challenging, but with a well-presented portfolio and resume, you can increase your chances of landing your first job in the field. Focus on highlighting your project examples, emphasizing your soft skills, customizing your resume, showcasing your work on GitHub, and seeking feedback. Good luck in your new career!

Twilio Verify Rate Limiting

2023-03-29T00:00:00Z

Twilio rate limits are used to apply limits to a category of requests.

Twilio Client Auth

Before interacting with the Twilio API, you will need to require the twilio-ruby gem and instantiate a @client using your account credentials.

require 'twilio-ruby'
account_sid = ENV['TWILIO_ACCOUNT_SID']
auth_token = ENV['TWILIO_AUTH_TOKEN']
@client = Twilio::REST::Client.new(account_sid, auth_token)

Creating Rate Limits

A rate limit is created with a unique_name (such as "account_rate_limit") and this unique name is used to reference the rate limit later.

rate_limit = @client.verify
  .v2
  .services(service_sid)
  .rate_limits
  .create(
    description: 'Account rate limit',
    unique_name: 'account_rate_limit'
  )
puts "Created Rate Limit"
puts rate_limit.sid

Within each rate limit category, limits are applied using buckets. A bucket is created to set a maximum number of requests over a period, using the format { max: N, period: S } for N maximum requests over a period of S seconds. Multiple rate limit buckets can be created for a rate limit which would each be applied to the requests within this rate limit group.

bucket = @client.verify
  .v2
  .services(service_sid)
  .rate_limits(rate_limit.sid)
  .buckets
  .create(
    max: 2,
    interval: 600 # 10 minutes
  )
puts "Created Rate Limit Bucket"
puts bucket.sid

Without creating a bucket, no rate limiting will be applied to the rate limit

Using Rate Limits

After a rate limit with zero or more buckets has been configured, requests will need to be associated with this rate limit when they are being created. The rate limit is referenced using the unique_name and a rate limit key.

verification = @client.verify
  .v2
  .services(service_sid)
  .verifications
  .create(
    to: user.mobile,
    channel: 'sms',
    rate_limits: {
      unique_name: rate_limit_key
    }
  )

The rate limit key should be a unique identifier on which the rate limit bucket rules should apply.

Multiple rate limits could also be applied to a request, such as per account, per country, or per group of digits within the recipient's mobile number.

.create(
  to: user.mobile,
  channel: 'sms',
  rate_limits: {
    account_rate_limit: user.id,
    country_rate_limit: user.country,
    # trim last 3 digits to get a block of phone numbers
    number_group: number_group(user.mobile)
  }
)

Rate Limit Error Codes

If a unique_name rate limit has not been correctly configured, the API will respond with a 60200 error.
If a request has been blocked by the buckets within a rate limit, the API will respond with a 20429 error.

References

Check the docs

Floating Point Arithmetic and Why It Makes Cents

2023-03-15T00:00:00Z

With the current headlines being dominated by the collapse of the Silicon Valley Bank, it seems apt to share this recent coding mistake I made with floating point numbers. My mistake did not cause and was not caused by the SVB collapse, but it occurred due to some work being done as a result of needing to modify systems that were previously built to use SVB.

As with many companies, we were regularly processing transactions through Silicon Valley Bank. We needed to quickly adjust our process to allow us to send the transfer through a different financial institution. Rather than taking the long route and modifying our whole payment process, I proposed to write a conversion script to run on the files generated by the existing system, as this would be quicker to implement, be lower risk for delivery, and have less chance of introducing new problems into the system, which has mostly been working well for years.

The setup for this file conversion is relatively standard as far as financial transfer files go. Ready through a 30-40 page PDF that outlines file structure and naming, which fields are required and the length and contents of each. Mostly boring details which are tedious, but important to get correct or the bank's system will reject the whole file and often not provide any useful error. As far as development cycles, it would be quite painful if we needed several iterations to diagnose and resolve an issue.

However, all of that boring stuff turned out to be straightforward, and after we discovered a particular naming convention we needed to follow, the converted files worked the first time.

The most pertinent detail in all of this was that our input file stored transaction values in decimal such as 40.62 where the new format used integers to store this same value in "cents" as 4062.

Enter the bug

We had run several tests using previous transaction files to ensure our script would generate files acceptable for the bank's systems to ingest and process and were feeling confident. However when we ran the conversion of the live data for payments, it was noted that there was a discrepancy in the total payment amounts.

The payment file included several hundred thousand dollars of transactions, but was short by $3.89.

Diagnosing the issue

Fortunately, I had also spent a few minutes writing a script to convert back while writing the conversion script. Doing this allowed me to diff the input file with a like-for-like display of what was included in the output file. This quickly highlighted where the problem was, which was everywhere, and what the problem was.

In the diff, this showed that the input value of 40.62 had been converted to 40.61. For exactly 389 transactions recorded in the payment file, the amount to be transferred was off by one cent ($0.01). This quickly triggered memories of floating point errors, with the popular claim that such and such programming language is bad because

0.1 + 0.2 == 0.3 // false
0.1 + 0.2 // 0.30000000000000004

Floating point arithmetic

Floating point errors can occur when computers represent real numbers with a finite number of bits. This can result in rounding errors and inaccuracies in calculations. While these errors may seem small, they can accumulate over time and lead to significant discrepancies in the final results.

Knowing what the problem was made it easy to pinpoint the line of software at fault. This line of code was able to correctly convert the dollar amount to cents most of the time. But had some cases like in the above, where the floating point representation of a number became "almost correct".

amount_in_cents = (amount.to_f * 100).to_i

The 'to_i' method in Ruby is used to convert the result of the mathematical operation 'amount.to_f * 100' to an integer. Which was the source of the problem, as sometimes this would result in a number just a little larger or smaller than the expected result. For numbers which were a little larger, the to_i function would truncate these, effectively rounding them down with worked in our favour. However for the numbers which were a little smaller, the to_i function would round them down a whole unit, so 40.62 would be converted to 4601.

The fix is in

To resolve this issue, we needed to explicitly round the result to the nearest integer, rather than truncating the number, which is accomplished in Ruby using the .round method.

amount_in_cents = (amount.to_f * 100).round

And then, after adding some tests to ensure these cases would forever be covered, a new file was generated and sent to the finance team for processing. The team checked the numbers and confirmed that everything added up.

A better solution

After some further research, it appears that Ruby provides a standard library for BigDecimal, which is actually the appropriate solution to use in this case. By casting our amount to a BigDecimal we can then apply our calculation of * 100 without losing precision.

amount_in_cents = (BigDecimal(amount) * 100).to_i

And as we have previously written unit tests covering these cases, we can be confident with our change.