Performance Engineering.

Profiling, p99 latency, memory leaks, CPU-vs-IO bound analysis, benchmarking, load testing, capacity planning, tracing. Covers 8 sub-skills.

• Performance Engineering · 1 of 3

  Distributed tracing, spans, OpenTelemetry

  Which HTTP request header carries the W3C-standard distributed-trace context?

  Ax-b3-traceidBx-trace-ctxCtraceparentDx-trace-id

• Performance Engineering · 2 of 3

  CPU-bound vs IO-bound diagnosis

  Compared with vmstat's 'us'+'sy' columns, what specific signal does vmstat's 'b' column add that helps tell CPU-bound from I/O-bound under the same load?

  ANumber of processes blocked waiting for futex wakeups in user codeBNumber of processes blocked waiting on uninterruptible I/OCNumber of processes blocked waiting for cgroup memory reclaimDNumber of processes blocked waiting on signal handlers to dispatch

• Performance Engineering · 3 of 3

  Microbenchmarks, JMH-style harness, variance

  JavaScript microbenchmark harnesses run the target function many times before the measured iterations begin. What is the primary reason?

  Ato let the OS scheduler move the process to a performance coreBso JIT compilation and optimisation tiering settle firstCto verify the result is deterministic before trusting the numbersDto force a GC pass so no collection pause lands in the window