Flux DB: Redis-Inspired Key-Value Store
Overview
A Redis-inspired key-value store built entirely from scratch in C++17 — no external dependencies, no shortcuts. Designed to understand and replicate the core internals of Redis at the systems level.
Key Technical Details
- Non-blocking event loop using
poll()-based I/O multiplexing with a pthreads worker pool for concurrent request handling - Incremental rehashing across two live hash tables, migrating keys in fixed batches of 128 per operation — eliminates the stop-the-world latency spikes found in naive resize strategies
- Sorted set backed by a parallel AVL tree and hash map sharing nodes via intrusive structs, enabling
O(log n)range queries andO(1)point lookups on the same underlying data - AOF persistence with configurable fsync policies for durability without sacrificing throughput
Performance
| Metric | Value |
|---|---|
| Throughput | 110k–150k ops/sec |
| p50 Latency | ~1µs |
| Sub-100µs Completion | 93–99% of requests |
Even with fsync-based AOF persistence enabled, the vast majority of requests complete under 100µs.