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SYSTEM DESIGNDesign a DNS SystemCloudflareAWS Route 53Google
TRAFFIC LEVEL
—/3
CONSTRAINTS
Queries/sec globally11.5M
Cached resolution latency< 1ms
Uncached (recursive) latency< 100ms
Record TTL range60 sec – 86400 sec
Cache hit rate~99% (most queries are for popular domains)
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
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CloudflareAWS Route 53Google

Design the Domain Name System — the internet's distributed directory that translates domain names to IP addresses. Handle 1 trillion DNS queries/day globally (11.5M queries/sec), resolve queries in < 10ms for cached entries, and support record types: A, AAAA, CNAME, MX, TXT.

📥 Assigned to:You — Senior Engineer
SCALE LEVELS
1
10,000 RPS
Target: <1ms
2
1,000,000 RPS
Target: <5ms
3
11,500,000 RPS
Target: <1ms
GLOBAL SUCCESS RATE
100.0%
P99 LATENCY
45ms
Target: < 200ms
TOTAL RPS INGESTED0 / 11,000
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