Codervai CP Platform

Competitive programming has a well-known attrition problem: students get access to a large problem bank, attempt problems that are too advanced for their current level, get frustrated, and drop out. The knowledge dependency tree is real — you can't reason about graph algorithms if you're still shaky on recursion.

The Codervai team — BUET CSE alumni and Google engineers — wanted a structured training program that enforced the right learning sequence without feeling like a rigid lockdown. They also needed streak tracking that held up under concurrent midnight submissions, where thousands of students rushed to maintain streaks before the daily reset.

The module unlock design uses temporal pacing rather than competency gating. Each cohort runs on a fixed schedule: module 1 from day 0, module 2 from day 7, and so on. All students see the same modules on the same calendar days — creating a shared experience that makes the Discord community useful rather than fractured across different curriculum points.

The streak concurrency problem required moving all logic to the database level. The naive approach — read the current streak, compute the new value, write it back — has a race condition when two submissions arrive for the same user within milliseconds. The fix was a single atomic SQL INSERT ON CONFLICT DO UPDATE with CASE logic: check whether yesterday was active, whether today has already been counted, or whether the streak needs to reset. No application code reads a value before writing.

The platform launched with structured curriculum cohorts. Students enroll, receive access to day-0 modules immediately, and watch new modules unlock on the cohort schedule. Each module contains curated problems with in-depth video editorial walkthroughs that explain reasoning and trade-offs rather than just showing the accepted solution.

Video encoding was optimized specifically for code content — dark IDE backgrounds with monospace syntax need higher sharpness settings than natural scenes. The resulting quality keeps code text legible even at lower bitrates on mobile connections.

The platform enrolled over 2,000 students across training cohorts. The temporal module structure kept students on a shared learning pace, which showed up in the Discord community as genuine peer learning rather than isolated struggles.

Streak tracking runs correctly under concurrent midnight submissions without any duplicate increments or missed streaks — the atomic SQL implementation handles concurrency transparently at the database level.