How monday.com redesigned its authorization system to cut P50 latency from 240ms to 6ms by using in-memory decisions.

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monday Engineering

monday.com redesigned its authorization system to handle scale by replacing real-time data enrichment with an in-memory, replication-based approach. The old system queried MySQL and multiple microservices on every request, adding ~200ms of latency and creating reliability risks. The new architecture uses WAL-based CDC pipelines to replicate data into DynamoDB and S3 snapshots, then loads tenant data into pod memory with a stickiness layer for consistent routing. The migration was done incrementally with continuous integrity checks. Results: P50 latency dropped from 240ms to 6ms, P99 from 720ms to 80ms, with full independence from tier 2–3 services and automated horizontal scaling.

Redesign Authorization to monday.com Scale