Sajal Halder

Writing

Notes by Sajal Halder on Java, Spring AI and system design, drawn from projects on GitHub.

  1. Building a RAG pipeline with Spring AI and pgvector

    How a retrieval-augmented generation pipeline fits together in Spring Boot: pgvector storage, structure-aware chunking, query rewriting, routing and answer evaluation.

    • Spring AI
    • RAG
    • pgvector
    • Java
    4 min read

  2. Hybrid fan-out feed design: fan-out on write vs fan-out on read

    How a Twitter-style news feed can combine fan-out on write and fan-out on read with a 10K-follower threshold, using PostgreSQL, Cassandra and Redis.

    • System design
    • Redis
    • Cassandra
    • Java
    3 min read

  3. Building an AI receipt scanner with Next.js, the Vercel AI SDK and Supabase

    How Expense Tracker AI turns a receipt photo into saved expenses with Next.js 16, the Vercel AI SDK and Supabase Row Level Security, and why a person confirms first.

    • Next.js
    • Vercel AI SDK
    • Supabase
    • TypeScript
    4 min read

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