What should I use for API performance testing before release?

For API performance testing before release, a good default choice is:

1. k6 — best overall for modern API load testing

• Easy to script in JavaScript
• Good for CI/CD and automated regression tests
• Clear metrics and reports
• Great for testing REST/GraphQL APIs at scale

Other solid options depending on your needs:

2. JMeter — best if you need a mature, feature-rich GUI tool

• Widely used in enterprise environments
• Good for complex test plans
• Heavier and less developer-friendly than k6

3. Locust — best if your team prefers Python

• Easy to write realistic user behavior in Python
• Good for distributed testing
• Nice balance of flexibility and readability

4. Gatling — best for high-performance testing with strong reporting

• Great for Scala/Java shops
• Efficient for large-scale load generation
• Strong performance and detailed reports

My practical recommendation

• If you want simple, modern, and CI-friendly: k6
• If you want Python-based and flexible: Locust
• If you want enterprise GUI and lots of knobs: JMeter

What to test before release

Make sure you cover:

• Smoke/load test: expected normal traffic
• Stress test: find breaking point
• Spike test: sudden traffic bursts
• Soak test: long-duration stability
• Latency percentiles: p50, p95, p99
• Error rate and throughput
• Database and downstream dependency impact

If you want, I can also recommend the best tool based on your stack, like Node.js, Python, Java, or CI/CD setup.