⏱ 8 min read A real-time location tracking system records device positions, supports geofencing, proximity queries, and stores movement history at scale. Core challenges: […] Read article

⏱ 7 min read A notification dispatch system routes outbound notifications — email, SMS, push, in-app — to the right channels based on user Read article

⏱ 7 min read Tenant onboarding provisions all the resources a new customer needs to use a multi-tenant SaaS product: creating their account, workspace, Read article

⏱ 7 min read A configuration management system stores, versions, and distributes application settings at runtime — feature flags, rate limits, connection strings, A/B Read article

⏱ 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 Real-time document collaboration lets multiple users edit the same document simultaneously, with each user’s changes appearing on others’ screens within 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 Search suggestion (autocomplete) returns candidate completions for a partial query in under 100ms. The system must handle millions of prefix 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 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 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 Token refresh is the mechanism by which a client exchanges a long-lived refresh token for a new short-lived access token, 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 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 health check endpoint lets load balancers, orchestrators, and monitoring systems determine whether a service instance is ready to receive Read article