Locust vs k6: Which Load Testing Tool for CI?
Locust scripts load tests in Python and scales with a distributed worker model; k6 uses JavaScript and is a lightweight, CI-native single binary.
Locust is a Python-based load tester where you define user behavior in code and scale via a master/worker model, with a live web UI. k6 (Grafana) is a Go binary scripted in JavaScript, optimized for low resource use and CI thresholds.
| Locust | k6 | |
|---|---|---|
| Scripting language | Python | JavaScript |
| Runtime | Python | Go (single binary) |
| Scaling model | Master/worker distributed | Single binary (k6 cloud for scale) |
| Live UI | Yes (web UI) | CLI + Grafana |
| CI fit | Good (headless) | Excellent (thresholds) |
In CI
k6 is a single binary with first-class CLI thresholds, which makes pass/fail gating in CI straightforward and keeps resource use low. Locust appeals to Python teams - behavior is plain Python - and scales horizontally via workers, which is useful for very high load, though its master/worker setup adds CI orchestration. Choose by language preference and how you intend to scale the load.
Run it in CI
Gate on thresholds (k6) or assertions (Locust) so regressions fail the build, and run distributed/high-load profiles on capable runners. Load generation is resource-heavy; larger, faster managed runners generate more load per runner and finish heavy runs sooner.
The verdict
Python team or need a distributed worker model for very high load: Locust. Want a lightweight single binary with clean CI thresholds: k6. Gate on thresholds/assertions in CI and size runners to the load you generate.