34. Delay Queue Scheduler
Millions of future actions — reminders, retries, expiries — must fire near their due time. Scanning everything every minute does not scale, and an in-process timer dies with the process.
Infrastructure & SREMedium
Designs
Pick a system. Work through the problem. Compare your approach.
Designs with worked examples 6
Ordered by design numberCompany tags are community-reported. Counts on cards show how many people reported that design.
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45. Design a Job Scheduler
Run 10,000 jobs a second within two seconds of their time, at least once, with retries, fairness between tenants and exactly-once effects.
ClassicMedium63. Design Real-Time Updates for Millions of Clients
Every goal on 25 million open apps within two seconds: SSE or WebSockets, pub/sub to the right server, resume by seq, hot topics, reconnect storms and push.
ClassicMedium69. Design Long-Running Tasks: Async Jobs with Progress and Results
Accept in milliseconds, work in the background: leases and heartbeats, retries and dead letters, progress by SSE and webhooks, fairness across tenants.
ClassicMedium80. Design a Message Queue like Amazon SQS
Build a queue around visibility leases and explicit acknowledgement, then add replicated partitions, FIFO groups, tenant fairness and bounded redrive: three self-contained interview boards.
ClassicMedium91. Design a CI/CD System like GitHub Actions
Turn 10 pushes a second into job graphs on ephemeral runners, with fair queues per pool, leases fenced by attempt and live logs.
ClassicMedium