For simple add/deduct inventory's quantity.

1. A event listener is created called AsyncUpdateInventoryQuantity and it listens to the UpdateInventoryQuantity event.
2. To make it queueable, this listener implements ShouldQueue indicating to Laravel that the job should be pushed onto the queue to run asynchronously.
3. This listener also implements ShouldBeUnique to ensure that only one instance of a specific job is on the queue at any point in time.
4. When the listener handle the job, it updates the quantity of the specific invetory with pessimistic locking lockForUpdate.

1. Git clone the project and change the working directory to the project root.
2. Run the command cp .env.example .env to define environment variables.
3. Install dependencies with composer install.
4. Generate app key with ./vendor/bin/sail artisan key:generate.
5. Make sure Docker is running. Then run ./vendor/bin/sail up -d to start and run the container.
6. Run DB migration and seeding ./vendor/bin/sail artisan migrate:fresh --seed.
7. Send a couple of API requests with curl --request POST --url http://localhost/api/inventories/random.
8. Run the worker manually ./vendor/bin/sail artisan queue:work.

1. API authentications and authorization are not handled in this demo app.
2. Rate limiting is following Laravel's default: max 60 attempts per minute by IP address.
3. If APIs were authenticated, uniqueId should be use and define the job unique key with sender's ID.
4. The API should return a unique request ID. With this ID the API sender can check the result of the sent API. (Out of scope for now)