How do you test WebSocket or real-time application performance?
- WebSocket
- real-time
- persistent connections
Answer it first, then compare. Nothing here is saved or scored.
Model answer
WebSockets maintain persistent connections, so the key metrics differ: connection count (how many simultaneous connections before failure), message latency (time from send to receive), message throughput (messages per second), reconnection behavior under network instability, and memory per connection on the server. Tools: k6 has WebSocket support, Artillery supports Socket.io, or custom scripts with ws library. Test both fan-out (one message to many clients) and fan-in (many clients sending simultaneously).
What interviewers listen for
- Workload modellingYou design the load shape from product traffic, not from tool defaults.
- Percentile literacyYou read p50/p95/p99 separately and explain why each matters.
- Bottleneck triageYou correlate metrics across application, database, and infrastructure layers.
- Capacity instinctsYou can translate a soak test into a sizing or scaling recommendation.