Season 01 · Day 9 of 28
Today: Await Missing in Fire-and-Forget
12 min · Easy · a focused fix, then field notes.
Next release Oct 24 · 00:00 UTC. Catch up anytime. Earlier accepted solves count. Weekly mission & rewards
Three fixes. Two days. One week.
Build permanent progress and earn rewards from accepted Practice work.
Debug the signal.
Ship the fix.
Production-shaped debugging labs across APIs, config, concurrency, and infrastructure. Reproduce the failure, follow the evidence, and prove the smallest safe change.
Try a debugging challenge without signing in. 3 guest labs are available; sign in for the full free catalogue and saved progress. Need a walkthrough? Open the guided starter.
Weekly Incident · Oct 19, 2026
One executable backend failure, a free debrief, and your next exercise.
Work-sample pack · Node.js
Backend reliability
Five multi-file investigations. A free debrief after each accepted fix. Pick up where you left off.
Choose a failure mode.
Focused bugs are targeted exercises; codebase incidents are deeper, production-shaped investigations with architecture, logs, and multiple layers. Search by symptom, then filter by lab type, source, status, or difficulty.
What are developers debugging?
Questions, dead ends, and useful investigation clues from real public Practice threads.
What developers are doing.
Recent public activity from developers who chose to share their Practice work.
More ways to practice.
Move from a focused drill to open-source history or company-style patterns when you want a different kind of debugging pressure.
Focused exercises
Train code review, system tracing, CI diagnosis, incident response, and fast debugging instincts.
Explore pathOpen-source labs
Practice against safely recreated public bug-fix history from the libraries that actually broke.
Explore pathCompany-style prep
Train backend and infrastructure failure patterns without affiliation claims.
Explore path