Platform EngineeringProblem 3 of 4
PlatformHardDeep Dive available
Design LeetCode
Design an online judge handling 50M submissions/day across 20+ languages. The hard parts: executing untrusted code safely in Firecracker microVMs with hardware KVM isolation and native snapshot warm-start (~25ms restore), real-time contest leaderboards with atomic Valkey Lua updates, post-contest Elo rating, and premium priority queues — all while keeping end-to-end latency under 5 seconds at 2K submissions/sec peak.
Key Topics
Firecracker microVM (Hardware KVM Isolation)Snapshot Warm Pool (Zero Boot Time)Diff Snapshot VM ResetPriority Queue (Kafka)Real-Time Leaderboard (Valkey)Elo Rating SystemKata Containers (K8s Integration)Premium Priority Queue