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SYSTEM DESIGNDesign a Banking Ledger (Double-Entry)StripePlaidJPMorgan
TRAFFIC LEVEL
—/3
CONSTRAINTS
Transactions/sec100,000
Ledger entries/sec200,000 (2 per transaction)
Accounts500M
ImmutabilityNo UPDATE/DELETE ever
Balance accuracyExact — no approximations
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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StripePlaidJPMorgan

Design an immutable double-entry accounting ledger for a fintech platform. Every financial transaction (transfer, fee, refund) must be recorded with full auditability. Account balances must be always accurate. Handle 100k transactions/sec and support queries: account balance, transaction history, reconciliation.

📥 Assigned to:You — Senior Engineer
SCALE LEVELS
1
1,000 RPS
Target: <100ms
2
10,000 RPS
Target: <50ms
3
100,000 RPS
Target: <20ms
GLOBAL SUCCESS RATE
100.0%
P99 LATENCY
45ms
Target: < 200ms
TOTAL RPS INGESTED0 / 11,000
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