Author name: techinterview.org

⏱ 7 min read A payment webhook receiver processes incoming HTTP callbacks from payment processors (Stripe, PayPal, Adyen) notifying your system of payment events: […] Read article

⏱ 8 min read Event replay re-processes historical events through a consumer to rebuild state, backfill a new downstream system, fix a processing bug, Read article

⏱ 7 min read An invitation system lets existing users invite new users via unique links or codes, tracking who invited whom and rewarding Read article

⏱ 8 min read API key management handles the full lifecycle of programmatic access credentials: creation, scoped authorization, usage tracking, rotation, and revocation. API Read article

⏱ 7 min read Search suggestion (autocomplete) returns candidate completions for a partial query in under 100ms. The system must handle millions of prefix Read article

⏱ 7 min read Connection pooling maintains a set of pre-established database connections that are reused across requests, rather than opening and closing a Read article

⏱ 8 min read Token refresh is the mechanism by which a client exchanges a long-lived refresh token for a new short-lived access token, Read article

⏱ 8 min read A WebSocket server maintains persistent bidirectional connections between clients and servers, enabling real-time push without polling. The challenge is not Read article

⏱ 8 min read A Bloom filter is a space-efficient probabilistic data structure that answers the question “is this element in the set?” with Read article

⏱ 7 min read A health check endpoint lets load balancers, orchestrators, and monitoring systems determine whether a service instance is ready to receive Read article

⏱ 8 min read Multi-region replication keeps data available and performant for users worldwide by maintaining synchronized copies of data in multiple geographic regions. Read article

⏱ 7 min read A bulk email system sends millions of marketing or transactional emails to user segments, tracking delivery, opens, clicks, and unsubscribes. Read article

⏱ 7 min read Consistent hashing distributes keys across a cluster of nodes such that adding or removing a node only remaps approximately 1/N Read article

⏱ 7 min read Two-phase commit (2PC) is a distributed transaction protocol that ensures all participants in a multi-node operation either all commit or Read article

⏱ 7 min read The inbox pattern is the receiving counterpart to the outbox pattern. Where the outbox ensures a service reliably publishes events Read article