IntermediateBEHAVIORAL
Describe a situation where you discovered a production performance bottleneck that involved both client-side and server-side components; how did you diagnose, communicate with stakeholders, and resolve it?
full stack
General

Sample Answer

We started getting dozens of complaints about slow page loads for our dashboard used by 5,000 daily active users. I pulled real user timing metrics and saw median TTFB spiking to 1.2s and frontend scripting adding 800ms. I ran flame charts and server traces, which pointed to a costly DB join and a heavy client-side React render caused by unbatched state updates. I flagged the issue to product and ops, estimated fixes (DB index + cached endpoint = 3 days; frontend memoization + batching = 2 days), and prioritized the backend change first. After deploying a new index and a Redis cache, TTFB dropped 60% and overall page load fell from 3.0s to 1.1s. The frontend optimizations cut CPU time by 55% on low-end devices.

Keywords

Used metrics (TTFB, flame charts, RUM) to diagnose both sidesCommunicated trade-offs and timelines to product and opsDelivered backend and frontend fixes resulting in 60% TTFB reduction and 55% client CPU improvement