Engineering notes
Engineering articles
What I learned building backends and AI systems for products with millions of users: the problems, the fixes and the trade-offs, with code you can reuse.
How we kept a backend fast at 300M+ users: indexes, Redis and RPC failover
How the DOP backend stayed fast at 300M+ users: finding slow MongoDB queries, compound indexes, Redis caching for read-heavy routes and failover across 5 RPC providers.
Read article →Scaling a Node.js API from 200K to 1M users with 60% faster responses
How the CV Maker backend grew from 200K to 1M+ users with about 60% faster APIs: MongoDB indexes, aggregation pipelines, response caching, pagination and safer errors.
Read article →How I built a WhatsApp and Telegram AI support bot with Claude in under 400 lines
How I built an open-source WhatsApp and Telegram AI support bot in Node.js: answers from your docs with Claude, saves leads, hands chats to a person. Design and code.
Read article →Why users get logged out at random, and how to fix JWT session bugs
Why users get logged out at random with JWT sessions, and how to fix it: refresh races between tabs, expiry and clock skew, cookie settings and secrets across servers.
Read article →Building AI agents with LangGraph and n8n: what works in production
Taking AI agents to production: when to use n8n, LangGraph or plain code, validating tool calls, evaluating before release, and keeping cost and latency down.
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