Practice real debugging, security, and system design on production-shaped code. Defend every decision in a replay.
replay/session_8842.log
$ codritium replay --challenge debug-mem-leak-prod-node
# session 8842 · 3 decision points · 1 redirect
[00:02:14] candidate: request streaming buffer; suspect Buffer.concat in hot path
[00:04:33] ai: suggests replacing with stream.PassThrough
[00:05:01] candidate rejects · reason: backpressure not handled in caller
[00:07:48] candidate proposes async iterator; ai validates
─────────────────────────────────────
result: root cause found in 7m48s · regressions (30d): 0%
defensibility (panel): 4.6 / 5
Outcomes
A small selection of the people who trained on Codritium and landed roles at the companies they wanted. Their words. Pause the row to read.
Priya N.
Software Engineer · Google
"Honestly? Before Codritium I was just clicking Accept on whatever Copilot suggested. The replay reviews made me watch myself do it — every accepted suggestion, every redirect I didn't push back on. Week three I started saying no out loud. The defensibility drills taught me how to explain *why* I said no. That's what got me through the Google panel. Offer landed six weeks after I started."
Marcus J.
SDE II · AWS
"Eight system design interviews. Bombed five before I found Codritium. The system design track here was the first place that made me admit I was memorizing tradeoffs instead of actually deciding them. The panel reviews — real senior engineers watching you reason through it live — broke that habit in about a month. When AWS asked about consistency models, I finally had a real answer instead of a script. Offer the next week."
Yuki S.
Software Engineer · Stripe
"Stripe's take-home almost broke me the first time I tried. Two years later I came back, but this time I'd spent six weeks on Codritium's take-home prep track and the panel-graded sessions. The rubric was in my head before I opened the doc. I knew which sections they'd skim and which they'd read line by line, because the replay reviewers here had already called out every weak pattern I had. Took the Stripe offer the day it landed."
Daniel O.
Senior Software Engineer · Meta
"Meta rejected me three times in five years. I'd done LeetCode, paid a coach, read every system design book — nothing moved. Two months on Codritium and the panel format finally clicked. The replay reviews showed me what 'defending a design choice' actually sounds like out loud, not on paper. Walked into round four at Meta and for the first time I had real answers. Different person walked out of that room. They made the offer."
Ananya R.
Member of Technical Staff · Anthropic
"The 'AI-rejection rate' thing sounded like jargon when I first joined Codritium. Eight weeks of sessions later I realized it's the whole skill. The pattern library taught me which AI suggestions were most likely to fail in production — and how to catch them before they shipped. Anthropic ran three rounds of 'why didn't you accept what the model suggested.' That's the job, and Codritium is the only place I've seen that actually teaches it. Offer in week ten."
Lucas P.
Software Engineer · Netflix
"I cried after my first Netflix panel. Ten years of winging it caught up with me in one afternoon. Spent the next two months on Codritium doing replay reviews and the Hard-tier challenges — watching real senior engineers think through real production bugs, then trying to do it myself. Second time around at Netflix the call lasted nine minutes. They made the offer at the end. I don't think I'd have gotten there without the replay format."
Sofia M.
Senior Engineer · Shopify
"My regression rate at work was embarrassing. The kind your manager pulls you aside about. Three weeks of Codritium's regression-rate drills and the heatmap showed me exactly where I was breaking things — distributed debugging, mostly. My PRs stopped bouncing the next sprint. Six months later a Shopify recruiter reached out, and by then I had the defensibility scores from the platform to back up my pitch. Offer signed in March."
Ravi K.
SDE · Microsoft
"Rejected at Microsoft last May. The recruiter literally said 'come back when you can defend your decisions better.' I didn't even know what that meant at the time. Codritium's panel reviews taught me — not by lecturing, but by making me defend my own replays out loud, week after week. Came back to Microsoft in April with answers I could actually back up. Same recruiter, same loop. Offer this time."
Emily L.
Software Engineer · OpenAI
"I'd been on every other prep platform — LeetCode, Pramp, AlgoExpert, all of them. Came to Codritium expecting more of the same. The replay format is different. You watch how senior engineers actually think through a problem, not just what they end up writing. The AI-pair patterns library showed me the three or four prompts that mattered for my OpenAI take-home. I used them. Offer landed two weeks after I submitted."
Tom W.
Senior Software Engineer · Datadog
"Was a senior at a startup nobody had heard of. Tried to switch and got ghosted by every Series B I applied to. Two months on Codritium changed that — the panel-graded sessions gave me language for my work, and the defensibility rubric gave me a way to talk about decisions instead of just outcomes. By November I could pitch myself without sounding like a junior. Datadog signed me on the spot after the panel."
The fast track
Most juniors never see how seniors actually think. So they never grow. Watch real senior dev replays. Practice the same problems. Skip years off the traditional path.
Juniors don't grow because they never face the problems seniors face. We show you. Every replay. Every decision. Every defense.
Watch how senior engineers solve real production problems. Step through their prompts, their pushbacks, their rejections. The work, not the polished result.
Traditional path: 2–3 years of being in the right rooms. Here: the same exposure, on real problems, without the wait.
Platform · Challenges
Every challenge is sourced from an actual interview loop at Google, Stripe, Meta, AWS, and others. No toy problems. Pick one. Defend your answer.
Category 01
Production bugs pulled from real interview loops. Node, Python, Go. Memory leaks, race conditions, silent data loss. Find the root cause. Prove it.
Category 02
OWASP-class bugs that ship past AI. SSRF in tool-using agents. Prompt injection as RCE. Auth drift in generated code.
Category 03
Take a 400-line component. Refactor it with an AI pair. Defend the decomposition in a panel review.
Category 04
A real backlog ticket. Ship it end to end. Tests, migrations, telemetry, PR description. Graded on the full rubric.
Why Codritium
What separates a senior engineer in 2026 isn't typing speed. It's deciding — and defending — what to keep, what to reject, and when to push back.
Challenges come from real incidents and real codebases. The bug you debug here looks like the one you'll hit at work next month.
Every session pairs you with an AI. You're graded on the loop. When to accept. When to reject. When to push the model harder.
Your session is a record. Every prompt. Every redirect. Every reasoning step. Re-watch your decisions or step through the panel's.
We measure what matters. Time to a correct fix. 30-day regression rate. A blind defensibility score. Not lines per minute.
Certifications
Three levels. Each reviewed by working engineers. You get a defensibility score, not a multiple-choice grade.
Entry credential. AI-assisted debugging. Code review with AI. Security awareness. Design defense via replay.
6 hours, 5-day window
See the rubricMid-career credential. Adds production incident response, AI-assisted refactoring at scale, and a live panel defense.
1-day proctored + 60m panel
See the rubricSenior credential. Security engineering against AI-generated code. Multi-system design defense. Contribution review.
2-day proctored + 90m panel
See the rubricCommunity
Not a forum. Replay reviews from working engineers. Panel-graded contributions. A leaderboard that ranks judgment, not vanity.
Watch how working engineers solved the same challenge. Step-by-step replays with timestamped commentary from the panel.
Open Replay CenterEngineers with the highest defensibility scores, longest zero-regression streaks, and most accepted contributions. Updated weekly.
See the board4,200+
Challenges shipped
across debugging, security, refactoring, and feature build
612
Contributing engineers
authors, reviewers, panel members
0%
Vanity metrics tracked
we score regressions, not commits
Weekly
Competitions
timed, panel-reviewed, ranked
Contributors program
Author a challenge. Get credited, paid, and reviewed by the panel.
Research
A first-class research program. We publish benchmarks of human + AI engineering pairs. Open rubric. Anyone can replicate.
Our first benchmark of human + AI engineering pairs. 4,200 tasks. 612 engineers. 14 production codebases. We measured time to a correct fix, 30-day regression rate, and a blind defensibility score across 12 task categories.
Benchmarks
Time to fix. 30-day regression rate. Defensibility score. Public. Replicable.
See the rubricReports
State-of reports on AI engineering, debugging, security, and code review.
Browse reportsStudies
Smaller, targeted studies on specific workflows. Panel-reviewed before publication.
See studiesNewsletter
One email. Replay breakdowns. Research previews. Challenge releases. No course upsells. Unsubscribe anytime.