Intermediate
Too many connections
A marketplace scaled its API to 100 servers and now the database refuses connections and reads are slow. Fix the data tier while keeping users' own changes visible.
Reads are ten times more frequent than writes. One read in ten is a user reloading something they just changed.
What your design must achieve
- Availability ≥ 99.9 %
- Latency p99 < 250 ms
- Stale reads < 2 %
- Infrastructure cost per month < 12,000 $ bonus