About

I’m Andrzej Karaś, a senior software engineer. Most of my career has been spent building and evolving SaaS products — backend services, browser extensions, web applications and the infrastructure behind them. I like owning a problem end to end: from technical design and implementation, through migrations and testing, to running it in production and fixing it when it misbehaves.

What I work on

• Backend & data processing — APIs, real-time communication, event-driven processing.
• Software architecture — evolving existing systems step by step instead of rewriting them: data models, module boundaries, safe migrations.
• Browser extensions — Manifest V2 and V3, service workers, shared foundations reused across extensions, extension ↔ backend communication.
• Testing & performance — from unit and integration tests to end-to-end, load and performance testing.
• Reliability & observability — isolating failures, diagnostics, logging and metrics, so production problems are found and fixed quickly.

About this blog

Notes and lessons from production work: real problems, trade-offs and what I would do differently next time.

Contact

The easiest way to reach me is LinkedIn. Code lives on GitHub; see also my side projects.