Sentry

Sentry catches errors in production and tells you the user who hit it, the browser they used, and the sequence of events leading up to it. Sentry catches errors in real-time and gives you everything you need to fix them. It's error tracking that actually works across every platform: JavaScript, Python, Go, Ruby, mobile, you name it.

Python-based backend. Sentry invented the modern error tracking category. Beyond exceptions, it does performance monitoring (slow transactions, database queries), session replay, profiling, and cron monitoring. SDKs for 100+ platforms. The free cloud tier is generous: 5K errors/month, 10K performance transactions, 500 session replays, 1 user. Paid starts at $26/mo (Team) for 50K errors, 100K transactions, unlimited members. Business at $80/mo adds SSO, custom dashboards, and higher quotas.

Self-hosting is possible but the license changed. Sentry uses a functional source-available license (FSL/BSL). You can run it, but you can't sell a hosted version of it. Self-hosting requires Docker Compose with 16GB+ RAM minimum. It's a real deployment. Solo developers: free cloud tier. It's enough for side projects and early-stage apps. Small teams: $26/mo Team plan, absolutely worth it. The time saved on a single production debugging session pays for a year. Medium to large: Business at $80+/mo for SSO and advanced features.

The catch: the free tier's 5K error limit gets eaten fast if you have noisy exceptions. Rate limiting and filtering are essential. Self-hosting is possible but heavy: Kafka, ClickHouse, Redis, Postgres, Snuba, Relay. Budget 8+ hours/month of ops. Most teams are better off paying for cloud.