Design a CI/CD Execution Platform
Design a multi-tenant CI/CD execution platform similar to GitHub Actions. Repository events trigger versioned workflow definitions containing dependency graphs of jobs. The platform schedules isolated execution, streams logs, stores artifacts and caches, protects secrets, supports cancellation and retry, and reports a durable final result. Explain control-plane and data-plane ownership, execution semantics, security boundaries, and recovery at scale.
Design a Webhook Delivery Platform
Design a multi-tenant webhook delivery platform. Producers submit an event and customer identifier; the platform resolves the customer's configured endpoint, signs and sends the request, retries transient failures for up to twenty-four hours, and exposes delivery status and replay controls. Explain the APIs, durable state, scheduling, tenant isolation, failure semantics, and operational behavior at billions of delivery attempts per day.
Design Slack
Design a Slack-like team messaging service. Users communicate through workspaces, public and private channels, and direct messages. The system provides low-latency live delivery, durable history, offline catch-up, multi-device read state, presence, typing indicators, search, and retention controls. Explain ordering, fan-out, partitioning, failure recovery, and how an MVP evolves to global scale.