Posts and interview questions tagged Payments.
A system design walkthrough of a payment system: idempotency, the double-entry ledger, exactly-once processing, and reconciliation with the provider.
A system design walkthrough of WhatsApp: WebSocket delivery, message ordering, delivery and read receipts, online presence, and group fan-out at scale.
A system design walkthrough of a news feed like Twitter or Facebook: fan-out on write vs read, the celebrity problem, ranking, and caching at scale.
A system design walkthrough of a notification system: multi-channel fan-out (push, SMS, email), queues, retries, dedup, and delivery at scale.
A system design walkthrough of a distributed cache like Redis/Memcached: consistent hashing, eviction policies, replication, and write strategies.
A system design walkthrough of a rate limiter: token bucket vs sliding window, where it lives, and making limits work across a distributed fleet.
A full system design walkthrough for a URL shortener like bit.ly: requirements, estimates, short-code generation, caching, and scaling to billions.
Most people fail system design interviews for lack of a method, not knowledge. Here's a repeatable framework to design any system in 45 minutes.
Production-grade React auth: short-lived JWT in memory, rotating refresh tokens, server-enforced RBAC, Azure AD via MSAL, OAuth2 + PKCE — real code.
Event-driven architecture in .NET: why choose it, problems solved, challenges, a full diagram, real ASP.NET Core + React code, and when NOT to use it.
Stream tokens, ground answers in your docs with RAG, and use pgvector — the production playbook for a ChatGPT-style app in React with real metrics.
Enterprise React feature-based architecture: why type folders break at scale, the 4 rules, full feature code, lazy-load splits, real before/after metrics.