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API – response time

techhadoop , , ,

Here are fast, reliable ways to measure client-side API response time (and break it down) — from your laptop or from an EKS pod.

1) One-shot timing (curl)

This prints DNS, TCP, TLS, TTFB, and Total in one go:

curl -s -o /dev/null -w '
{ "http_code":%{http_code},
  "remote_ip":"%{remote_ip}",
  "dns":%{time_namelookup},
  "tcp":%{time_connect},
  "tls":%{time_appconnect},
  "ttfb":%{time_starttransfer},
  "total":%{time_total},
  "size":%{size_download},
  "speed":%{speed_download}
}
' https://api.example.com/path

Fields

  • dns: DNS lookup
  • tcp: TCP connect
  • tls: TLS handshake (0 if HTTP)
  • ttfb: time to first byte (request→first response byte)
  • total: full download time

2) From EKS (ephemeral pod)

Run N samples and capture a CSV:

kubectl run curl --rm -it --image=curlimages/curl:8.8.0 -- \
sh -c 'for i in $(seq 1 50); do \
  curl -s -o /dev/null -w "%{time_namelookup},%{time_connect},%{time_appconnect},%{time_starttransfer},%{time_total}\n" \
  https://api.example.com/health; \
done' > timings.csv

Open timings.csv and look at columns: dns,tcp,tls,ttfb,total. Large ttfb means slow upstream/app; big tls means handshake issues; big gap total - ttfb means payload/download time.

3) Separate proxy vs upstream (Kong in the path)

Kong adds latency headers you can read on the client:

curl -i https://api.example.com/path | sed -n 's/^\(x-kong-.*latency\): \(.*\)$/\1: \2/p'
# x-kong-proxy-latency: <ms>   (Kong → upstream start)
# x-kong-upstream-latency: <ms> (Upstream processing)

These help you see if delay is at the gateway or in the service.

4) Quick load/percentiles (pick one)

  • hey hey -z 30s -c 20 https://api.example.com/path
  • vegeta echo "GET https://api.example.com/path" | vegeta attack -rate=20 -duration=30s | vegeta report
  • k6 (scriptable) // save as test.js import http from 'k6/http'; import { check } from 'k6'; export const options = { vus: 20, duration: '30s', thresholds: { http_req_duration: ['p(95)<300'] } }; export default () => { const r = http.get('https://api.example.com/path'); check(r, { '200': (res)=>res.status===200 }); }; Run: k6 run test.js

5) App-level timers (optional)

Add a Server-Timing header from the API to expose your own phase timings (DB, cache, etc.). Then the client can read those headers to correlate.

6) Common gotchas

  • Proxies can add latency; test both with and without proxy (NO_PROXY / --proxy).
  • Auth: measure with real headers/tokens; 401/403 will skew.
  • SNI/Host: if hitting by IP, use --resolve host:443:IP -H "Host: host" so cert/routing is correct.
  • Warmup: discard first few samples (JIT, caches, TLS session reuse).

If you want, share a few curl -w outputs from local vs EKS and I’ll pinpoint where the time is going (DNS/TLS/TTFB/payload).