SYSTEM DESIGNDesign a Rate LimiterAWSCloudflareStripe
TRAFFIC LEVEL
—/3
CONSTRAINTS
Per-user limit100 req/min
Per-API-key limit1,000 req/min
Global limit10M req/min
API servers100 nodes
Latency budget< 5ms overhead
Compute & Network
Load BalancerDistribute traffic
API GatewayEntry point / auth
API ServerBusiness logic
Worker NodeAsync processing
CDN EdgeGlobal cache
WebSocket GatewayPersistent connections
Data Stores
PostgreSQLRelational DB
MySQLRelational DB
CassandraWide-Column DB
DynamoDBNoSQL / Managed
S3 BucketObject storage
Queues & Cache
Redis CacheIn-memory store
KafkaEvent stream
ZookeeperCoordination
Specialized
Bloom FilterProbabilistic set
Rate LimiterThrottling
Geohash ServiceGeospatial index
Trie ServerPrefix search
APNS / FCMPush notifications
AggregatorBatch / roll-up
Drag to canvas · Hover node for × to delete · Draw from handle to connect
Design your architecture
Drag components from the left panel · Connect them by drawing from a node handle · Hit Start Simulation to validate
🚨 INCIDENT
AWSCloudflareStripe

Design a rate limiter that enforces API quotas: 100 requests/minute per user, 1000 requests/minute per API key, and global 10M requests/minute. The limiter must add < 5ms latency and work across a distributed fleet of 100 API servers.

📥 Assigned to:You — Mid Engineer
SCALE LEVELS
1
100 RPS
Target: <5ms
2
10,000 RPS
Target: <10ms
3
100,000 RPS
Target: <3ms
GLOBAL SUCCESS RATE
100.0%
P99 LATENCY
45ms
Target: < 200ms
TOTAL RPS INGESTED0 / 11,000
EngPrep — Real Engineering. Real Interviews.