GraphQL API load testing made simple

The challenges of load testing GraphQL

GraphQL flips the assumptions most load testing tools are built on. Four things that make it harder than a plain REST endpoint:

• One URL, many operations. Every request hits the same endpoint. A tool that aggregates per-URL gives you a meaningless combined stat.
• Queries vs mutations behave differently. Reads and writes stress different layers of your stack. Averaging them hides the actual bottlenecks.
• Field resolvers can be nested and slow. A single query can trigger a cascade of backend calls. Naïve load tests miss the N+1 problem entirely.
• Auth often involves short-lived tokens. Bearer tokens, signed requests, scoped session headers. Static headers in your load tester won't cut it.

Automatic GraphQL detection in Clobbr

When you set up a run, Clobbr inspects the payload. If it sees a GraphQL shape (a query or mutation field in the body), it switches into GraphQL mode. That means:

• Stats are tracked per operation, so a slow mutation doesn't hide behind fast queries.
• The UI shows the operation name and type alongside timings, so you're reading a chart, not decoding JSON.
• Historical comparison across runs works per-operation too, handy when you land a resolver change and want to see if p95 moved.

You don't flip a toggle or pick a mode. Just paste your payload.

Setting up a GraphQL load test in Clobbr

The fastest path, start to finish:

• URL: paste your GraphQL endpoint (e.g. https://api.example.com/graphql).
• Verb: POST (GraphQL over HTTP uses POST by convention).
• Headers: set Content-Type: application/json and your auth header.
• Payload: drop in a JSON body with your query and variables.
• Iterations: start with 100 sequential to see latency, then re-run at 500 parallel to see concurrency behavior.

Interpreting query vs mutation stats

With per-operation stats in front of you, the signal sharpens. Typical patterns:

• Query p50 low, p95 spikes: one or more resolvers is triggering an unbatched DB call. Look at DataLoader usage or N+1 suspects.
• Mutation p50 higher than query p50: normal. Writes hit the database and your write-path caches.
• Mutation p95 ≫ query p95: lock contention or write amplification. Increase concurrency in Clobbr and look for non-linear degradation.
• Parallel run fails where sequential passed: your service has a concurrency bottleneck: connection pool, worker count, or a shared mutex.

Authentication headers for GraphQL

Static headers work for a session token pasted in during a local test. Anything else, like a JWT with a short TTL, a signed header, or per-request session rotation, benefits from Clobbr's scripted headers. Write a tiny inline script that computes or refreshes the header before each iteration batch, and you won't hit 401s mid-run.