Fluent English Course: a language-learning app with an AI teacher
- Problem
- Students practice speaking and writing between lessons, but teachers can't review every answer quickly. Feedback came late, or not at all.
- What students get
- Immediate, detailed feedback on every answer, like a personal teacher. In speaking tasks the AI teacher listens, shows what the student said, corrects it, explains why, and asks a follow-up question. The feedback is about each student's own answer, so everyone works on their own mistakes. A level test, graded by AI, places new students at the right level.
- What I built
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- A student app (iOS, Android, web) with topics, grammar, business projects, vocabulary and speaking tasks.
- One AI pipeline for 7 task types: Deepgram transcribes audio, then Claude gives feedback on speaking, writing, grammar and business-project drafts.
- Prompts live in the database, so managers edit them in the app. Every save makes a new version, and each answer records the version it used.
- Key decision
- Reliability first. The client creates the answer's id, so a double submit gives one answer. A database trigger starts the work, and a sweeper every 2 minutes retries stuck or failed answers, up to 5 attempts with backoff. A claim with a lease means two runs never answer the same row.
- Stack
- Expo / React NativeTypeScriptSupabaseEdge Functions (Deno)Claude APIDeepgrampg_cron