BlitzCode

//overview

//stack

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// what BlitzCode is built with
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const stack = {
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frontend: ["React", "TypeScript"],
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backend: ["Next.js API Routes", "TypeScript"],
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queuesCache: ["BullMQ", "Redis", "localStorage"],
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api: ["gemini", "deepseek", "mistral", "judgeO", "codeforces", "leetcode"],
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database: ["Postgresql", "Drizzle ORM"],
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tools: ["NextAuth", "Bun", "WebSockets"],
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} ;
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export default stack;

//preview1 file

zoom

//how it works

1. 01

   Choose how to play

   Select single-player to practice on your own, or multiplayer to compete against another player in a real-time match.

2. 02

   Get a quiz

   In single-player mode, BlitzCode fetches questions from the backend based on your selections and displays them for you to play.

3. 03

   Match with another player

   In multiplayer mode, BlitzCode connects over WebSockets and looks for another player who selected the same quiz options. Once matched, both players play in real time.

4. 04

   Generate questions when needed

   If the database has too few questions for a selected combination of options, background workers can ask an LLM to generate new questions and save them to the database.

5. 05

   Practice DSA problems

   Choose from nearly 3,000 problems, write a solution in the editor, run it against public test cases, and submit it against private test cases.

//features7 total

1. Single-player quizzes

   Fetch questions based on your selected options and practice at your own pace.

2. Real-time multiplayer

   Compete live with another player through WebSocket matchmaking that pairs players with the same selected quiz options.

3. LLM-generated questions

   When the question bank is short for a selected combination, workers can generate and store new questions using an LLM.

4. A large DSA problem library

   Practice with nearly 3,000 problems, rated by Codeforces difficulty and covering different concepts.

5. In-platform code editor

   Write and run solutions without leaving BlitzCode. Test against public cases, then submit against private test cases.

6. Complexity graphs

   After submitting a problem, view a graph of your solution’s time and space complexity.

7. LeetCode and Codeforces integrations

   Connect your profiles to bring your coding activity and BlitzCode progress together.

//problems & fixes

• Keeping multiplayer matches fair

  −Problem: Players need to compete on equivalent quizzes for a multiplayer match to be fair.

  +Solution: WebSocket matchmaking pairs players who selected the same quiz options before starting a real-time game.

• Not enough questions for every quiz combination

  −Problem: The question bank may not have enough questions for a particular combination of selected options.

  +Solution: Background workers can request new questions from an LLM and store them in the database for use in quizzes.

• Handling LLM failures and token limits

  −Problem: An LLM provider may fail or reach its token limit while generating a question.

  +Solution: Use three LLM API keys with fallback between providers so generation can continue when one provider fails or reaches its limit.

• Processing many question-generation jobs

  −Problem: A burst of jobs to generate or store questions can overwhelm a single worker.

  +Solution: Run multiple concurrent workers so jobs can be processed in parallel.