For developers, who are building real-time data-driven applications, Redis is the preferred, fastest, and most feature-rich cache, data structure server, and document and vector query engine.

Adaptive Radix Trees implemented in C

MPack - A C encoder/decoder for the MessagePack serialization format / msgpack.org[C]

CUDA based Voxel Raycasting - Paper: Efficient, High-Quality, GPU-Based Visualization of Voxelized Surface Data

An unreal engine plugin with an embedded HTTP server to do your bidding.