Event Sourcing

Series Navigation: This is Part 3 of the Core Banking Systems Architecture Masterclass. ← Previous: Part 2 — Distributed SQL ACID Latency | Master Curriculum Hub | Next: Part 4 — Saga Pattern → | Pillar Hub: Banking Microservices Architecture Event Sourcing & CQRS: Immutable Ledger for Microservices Answer-first: Event Sourcing and CQRS resolve the fundamental architectural tension in core banking between immutable auditability on the write path and ultra-low latency on the read path. By treating append-only domain event streams as the single source of truth and publishing via NATS JetStream transactional outbox pipelines, core platforms eliminate dual-write hazards and achieve sub-millisecond balance projection latencies. ...

Prerequisite: Mastery of microservices architecture, event-driven domain modeling, Event Sourcing invariants, and distributed transaction patterns. Banking Microservices Architecture: Event Sourcing & Saga Answer-first: Modern core banking architecture transitions legacy monolithic mainframe deployments into decoupled event-driven microservices utilizing Event Sourcing for immutable transaction history, Command Query Responsibility Segregation (CQRS) for microsecond balance queries, and Saga Orchestration patterns with compensating transactions to guarantee eventual consistency across distributed banking sub-domains without two-phase commit overhead. ...

Core Banking Systems Architecture Masterclass Guide Answer-first: Modern cloud-native core banking transitions from batch-driven mainframes to composable distributed platforms: immutable double-entry ledgers enforcing mathematical zero-drift balance invariants, multi-region Distributed SQL guaranteeing serializable ACID transactions, event-sourced CQRS projections, orchestrated compensation Sagas, zero-allocation ISO 20022 streaming, and FAPI 2.0 security. This architecture eliminates end-of-day batch freezes, delivering sub-25ms P99 latency across active-active deployments. Prerequisite: Practical familiarity with distributed systems fundamentals, relational transaction isolation levels (ACID), event-driven microservice patterns, and enterprise networking (mTLS, TCP/IP, gRPC). For foundational context, explore our Banking Microservices Architecture and Go Microservices Guide. ...