Latest Blog Posts

Insights, tutorials, and experiences from my journey in software development and technology.

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Popular:

AI Engineering

Backend

CI/CD

Concurrency

Debugging

Distributed Systems

Engineering Practice

Evaluation

A Passing Test Only Proves the Test Passes

Testing

CI/CD

Shailesh Chaudhari2026-08-23

9 min read

A Passing Test Only Proves the Test Passes

Real examples of tests that passed against code the framework never loaded, assertions that silently matched nothing, a CI pipeline with no test job, and a mutation harness that reported a perfect score. Plus the habit that catches this class of bug.

Why We Didn't Use Redis for Webhook Deduplication

Idempotency

Webhooks

Shailesh Chaudhari2026-08-23

10 min read

Why We Didn't Use Redis for Webhook Deduplication

A technical walkthrough of KhataGO's WhatsApp webhook pipeline: why at-least-once delivery makes deduplication mandatory, why SETNX splits the claim from the truth, why a duplicate must return 200 and not 500, and what a claim without an expiry costs you.

My Mutation Score Was 100%. That's How I Knew Something Was Wrong.

Testing

Mutation Testing

Shailesh Chaudhari2026-08-23

8 min read

My Mutation Score Was 100%. That's How I Knew Something Was Wrong.

A real debugging story: why a 100% mutation score meant the harness was broken, not the tests. How mutation testing actually works, why an already-failing suite kills every mutant, and the general lesson about tools that grade other tools.

Concurrency

PostgreSQL

Shailesh Chaudhari2026-06-13

13 min read

Building an Inventory Engine That Never Oversells Under Concurrency

A deep dive into concurrency control for inventory: the read-then-write race that causes overselling, three database strategies to prevent it (atomic conditional update, pessimistic locking, optimistic versioning), deadlock-safe multi-item baskets, idempotent placement, hot-SKU sharding, and a chaos test that proves it fails closed.

Production RAG That Says "I Don't Know" Instead of Hallucinating

RAG

AI Engineering

Shailesh Chaudhari2026-06-13

12 min read

Production RAG That Says "I Don't Know" Instead of Hallucinating

Most RAG demos look great until real users hit them, then they hallucinate, re-embed everything on every deploy, and you have no way to tell if a prompt change made things worse. Here's how I built Grounded to do the reliable parts right: a retrieval-score guardrail that refuses to answer, content-hash idempotent ingestion, retry-with-backoff, cited answers, and a CI eval harness.

Idempotency

Payments

Shailesh Chaudhari2026-06-15

11 min read

Idempotency Keys: Making Money-Moving Endpoints Safe to Retry

A practical deep dive into idempotency keys for payment and write APIs: why retries cause double-charges, the claim-run-complete protocol that collapses concurrent retries to one execution, fail-fast vs wait-and-replay, releasing the key on failure, the fingerprint-mismatch guard Stripe uses, TTLs, and where the one atomic step really lives. Built around idempotency-kit, a zero-dependency TypeScript library.