01. Full Stack Ecommerce Checkout Web AppA production checkout brief where vague specs collapse under real commerce edge cases.Full-stack & webNext.js 16web—intermediate10 / 12m
02. Team Invites + Role ManagementSaaS settings workflow with hidden lifecycle and permission traps.Domain workflowsNext.js 16web—expert5 / 18m
03. Idempotent Payment WebhooksRetries, ordering, and atomicity are the product.Backend & APINode.js APIapi—expert5 / 22m
04. Messy CSV ReconciliationTurn inconsistent exports into an explainable ledger.Data & MLPython pipelinepipeline—intermediate5 / 20m
05. Resumable File Sync CLIA CLI tested through interruptions and repeat runs.Systems & CLINode.js CLIcli—expert5 / 24m
06. Rate Limit + Abuse ControlsReliability controls correct at boundaries and under concurrency.Security & reliabilityHTTP serviceapi—expert5 / 20m
07. Rate LimiterA limit per client and one method. Identity and exact window boundaries are the whole game.Security & reliabilityTypeScriptlibrary—expert3 / 10m
08. Charge ProcessorA processor, one method, a request key. What happens when the same request arrives twice is the whole game.Backend & APITypeScriptlibrary—expert3 / 10m
09. Buried AnswersA search function, a pile of docs, a question. Whether it surfaces the real answer is the whole game.Data & MLPythonlibrary—expert3 / 11m
10. Interest AccrualPrincipal, a rate, two dates, one number. How you count the days between them is the whole game.Domain workflowsTypeScriptlibrary—expert3 / 10m
11. Fixed-Block Pool AllocatorThree functions in C. The memory you forget to give back is the whole game.Systems & CLIC compilerlibrary—expert3 / 12m
12. The Guest ListThree tables and a count. The constraints you forget are the bugs in production.Backend & APISQLite 3database—intermediate3 / 11m