Developer Day: One working day as a software developer on a real-looking codebase, with AI teammates.

Developer Day puts you on a product team for one working day, 09:00 to 18:00. A tech lead, a product manager, QA, on-call and teammates send you work: a bug report with a failing test, a feature ticket, a slow endpoint, a teammate's pull request to review. You read the code, run the tests, branch, fix, commit, push and open a pull request, answer the review and merge once CI is green. Ship a bug and it comes back in the afternoon as an incident. Every play plants different bugs from the codebase's catalog, so no two days are the same.

One working day, about 3 hours · Python or TypeScript · solo or a team of up to 3 · $10 for one codebase, $15 for two, $18 for all three (from ₹981.76 incl. GST) · 6 plays per codebase · adding a codebase later costs the difference · Start

Three codebases

• ShopCart (Orders and catalog for an online shop): Discounts that must add up to the cent, a best-sellers list, product search as you type, a product cache and stock that two shoppers try to buy at once. Teaches: Hash maps and sets, Heaps for top-K, Tries and binary search, LRU caches, Pagination edge cases, Integer money.
• RideRoute (Dispatch and routing for a delivery fleet): Shortest routes on a road graph, matching drivers to pickups, merging delivery windows, finding nearby drivers fast and a rate limiter in front of the API. Teaches: Dijkstra and BFS, Priority queues, Interval merging, Spatial bucketing, Topological sort, Sliding windows.
• LedgerPay (Payments and reconciliation for a fintech): Money in minor units, payments that must not be charged twice, matching the bank's statement against the ledger, fraud windows and linked accounts. Teaches: Integer money, Idempotency keys with expiry, Two pointers on sorted streams, Interval overlap, Union-find, Retry state machines.

Your day

1. 09:00 · Onboarding: The tech lead points you at the repository, how to run the tests and the team's conventions.
2. 09:15 · Stand-up: Pick up your ticket, say how you'll approach it and name anything that blocks you.
3. Morning · The bug ticket: QA sends a failing case and a stack trace. Reproduce it, branch, fix it, add a regression test and open a pull request.
4. Late morning · The slow endpoint: On-call sees response times jump after yesterday's deploy. Read the profiler and the logs, then find the slow loop (Developer and Senior).
5. Midday · The feature ticket: The product manager wants something new. Pick the right data structure: hidden tests and a speed budget check it.
6. Afternoon · Code review: The tech lead comments on your pull request line by line. Reply, push fixes and get it approved. Review a teammate's pull request too.
7. 16:00 · The incident: If you merged a bug, it pages you now. Hotfix it, and at Senior level write the postmortem. Clean work means no page.
8. 17:30 · Wrap-up: Tell your manager what shipped and what is left. At 18:00 your debrief and your ending open.

Levels

• Junior Developer: One bug, one feature and a code review. Hashing, sorting, two pointers, stacks and binary search. Branch, commit, pull request.
• Developer: Adds the slow endpoint, a regression test with every fix, a teammate's pull request and a design discussion. Heaps, tries, BFS, intervals.
• Senior Developer: Adds a race condition, a merge conflict, owning the incident and leading the design call. Dijkstra, union-find, dynamic programming.

Your tools

• Code editor: The whole repository in the browser, with search, jump-to-line from stack traces and a diff of your changes.
• Terminal and git: status, add, commit, branch, checkout, push, merge, rebase, stash, log and diff, plus the test runner.
• Pull requests: Write the description, see the diff split or unified, read CI checks, reply to line comments and merge.
• Tracker: A team board with your tickets. In a team, take a ticket or, as the lead, assign one.
• Logs and profiler: Request logs, stack traces, a profiler and a latency chart that point at the real file and line.

What is graded

• 60% is checked by code: hidden tests for every ticket (including the cases you can't see), the speed budget on large inputs, whether your regression test fails on the old code and passes on yours, and your git hygiene (a branch, the ticket key in the commit, a focused diff, no debug prints, no skipped tests).
• 40% is judged: your pull request descriptions (what, why, how you tested it, the risk), your replies to review comments, your stand-up and design answers, your reviews of a teammate's code and, at Senior, the postmortem.
• Conduct counts: pushing straight to main, disabling a failing test or pasting a secret into chat costs points and can decide your ending.
• Every finished play keeps a debrief: what was planted, what you found or missed, the incident chain if there was one, the worked fix for each ticket, your ending and a certificate.

Your code never runs on our servers. Tests you run while you work run in your own browser; CI runs your code in an isolated sandbox with no network access and strict time and memory limits.

Questions

How long does a play take?

The day runs from 09:00 to 18:00 game time, about three hours in real time. You can take a break and come back: each play has 45 days from its start.

What do I get for one purchase?

Each codebase you own gives you two plays at each of the three levels: six plays, each with a fresh set of planted bugs.

Python or TypeScript?

Either. You pick the language when you start a play, and it doesn't change the price. The codebase, tickets and tests are the same in both.

Can I add a codebase later?

Yes. You only pay the difference between what you own and the bigger bundle.

Can I play with others?

Yes. Each play lets you invite two people, so a team of up to three shares the repository, the pull requests and the board, with a working copy each. You review each other's code. Solo players get AI teammates instead.

Do I need to install anything?

No. The editor, terminal, git, pull requests and the test runner all work in the browser.

Is it included for universities?

Yes. Members of an organization whose Bartman bundle includes simulations can play every codebase without buying.

Something looks wrong. Who do I tell?

Use Report a problem from the task or the debrief, or write to team@bartman.ai.