Design Distributed Counters
Medium · System Design · about 45 minutes
Asked at Meta, X (Twitter), ByteDance, Reddit, Snap.
Design a service that counts likes, views and reactions at scale: ~1M increments per second overall, with a single viral post receiving 100k+ increments per second. Counts are read ~10M times per second as feeds render; they may lag a few seconds, but must converge to the exact value and never lose increments.