Home Made CobbleDB Replaces DynamoDB at Perplexity to Cut Query Latency 5x

Perplexity replaced DynamoDB with its own Rust key-value store, and the numbers are hard to argue with: median batch-read latency 31.4ms to 5.60ms, p99 123ms to 24.2ms, storage costs down at least 20%. Cost was not the only driver - DynamoDB hides partition placement and caching, which makes tail latency impossible to reason about. 40,000 lines of Rust in two months, two engineers plus a swarm of coding agents.