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1. AI & ML·Tutorial

   Building a RAG Pipeline That Actually Works: Chunking, Embeddings, and Evaluation

   Build a RAG pipeline that holds up in production: chunking strategies, embeddings in pgvector, hybrid search with RRF, reranking, citations, and evaluation. · Yahia Rachek

   • CREATE EXTENSION IF NOT EXISTS vector;

     sql · line 1§ A table for chunks

2. Backend·Guide

   REST API Design Best Practices: Building APIs Other Developers Love

   A practical guide to REST API design: resource URLs, status codes, RFC 9457 errors, keyset pagination, idempotency keys, ETags, versioning, and rate limits. · Yahia Rachek

   • Fetching `limit + 1` rows reveals whether another page exists without a count query. The cursor is validated like any other input. Opaque means clients mustn't parse it, so you …

     text§ Keyset pagination in PostgreSQL

   • Never return 200 with an error in the body; retries, monitoring, and client libraries all key off the status. Prefer 404 over 403 when admitting a resource exists would leak inf…

     text§ Status codes that matter

3. React·Deep dive

   React Server Components Explained: When to Use Server vs. Client Components

   Learn how React Server Components work, what the use client directive really marks, and how to fetch, stream, and mutate data safely in the Next.js App Router. · Yahia Rachek

   • - **Fetching in `useEffect` out of habit.** If an API route exists only to feed one Client Component, fetch in a Server Component parent and pass the data down as props.

     text§ Common mistakes

4. Backend·Comparison

   JWT vs. Sessions: Choosing an Authentication Strategy for Your API

   How server-side sessions and JWTs work, what stateless auth really costs, how to revoke and store tokens safely, and when I choose each one for an API. · Yahia Rachek

   • return (await redis.exists(`denied:${jti}`)) === 1;

     ts · line 11§ A denylist keyed by jti

5. Java·Deep dive

   Java Virtual Threads in Practice: Scaling Blocking Code Without Going Reactive

   Learn how Java virtual threads scale blocking code: how they work, a runnable HttpClient fan-out, pinning, ThreadLocal pitfalls, and Spring Boot setup. · Yahia Rachek

   • - **Memory multiplied by thread count.** A thread local's value exists once per live thread: cheap with 200 threads, expensive with a million. `InheritableThreadLocal` values ar…

     text§ ThreadLocal pitfalls and scoped values

   • A pool exists to share something scarce, and virtual threads aren't scarce. Create one per task. To limit how many tasks touch a resource at once, limit the resource directly, a…

     text§ Creating virtual threads

6. Backend·Deep dive

   Database Indexing Explained: How B-Tree Indexes Really Speed Up Your Queries

   How PostgreSQL B-tree indexes work, how to read EXPLAIN plans, and how to design composite, covering, partial, and expression indexes that actually get used. · Yahia Rachek

   • If `CREATE INDEX CONCURRENTLY` fails (a deadlock, a uniqueness violation, a cancellation), it leaves an invalid index that queries ignore but writes still maintain. Find leftove…

     text§ Building indexes without blocking writes

   • Redundant prefixes are subtler. Once `(customer_id, created_at)` exists, an index on `(customer_id)` alone is usually dead weight, but because it's smaller, the planner may keep…

     text§ Finding unused and duplicate indexes

   • CREATE EXTENSION IF NOT EXISTS pg_trgm;

     sql · line 3§ Common indexing mistakes

7. Backend·Guide

   Microservices Communication: Synchronous vs. Asynchronous Patterns

   When to call a service directly and when to send a message, plus timeouts, retries, circuit breakers, idempotent consumers, the outbox pattern, and sagas. · Yahia Rachek

   • If the process crashes or the broker is down after the insert, the order exists but nobody hears about it. Publish first and you get the reverse: an event for an order that was …

     text§ The dual-write problem and the transactional outbox

8. DevOps·Tutorial

   Zero-Downtime Deployments with Docker and GitHub Actions

   Ship zero-downtime deployments with Docker and GitHub Actions: graceful shutdown, readiness checks, blue-green with Compose and Caddy, and safe migrations. · Yahia Rachek

   • - The previous release's image tag still exists in GHCR.

     text§ Pre-deploy checklist

9. Backend·Guide

   Caching Strategies with Redis: Cache-Aside, Write-Through, and When to Use Each

   A practical guide to Redis caching in TypeScript: cache-aside, TTL jitter, safe invalidation, write-through, write-behind, stampede fixes, and eviction. · Yahia Rachek

   • It needs no coordination, but it only helps while the key exists. A cold or just-deleted key still needs the lock or coalescing, which is why I layer them.

     text§ Probabilistic early expiration