LeetDezine — System Design and Internals
Event-Driven Patterns
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    1. Home
    2. Concepts
    3. Event-Driven Patterns
    08

    Concepts

    Event-Driven Patterns

    The patterns that make distributed systems reliable — from the dual-write problem to guaranteed event delivery across service boundaries.

    Event Sourcing
    Store state as a sequence of events instead of a current snapshot. Every state transition becomes auditable and replayable.
    Event LogReplayAudit TrailSnapshots
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    CQRS
    Separate the write model from the read model. Read replicas, projections, and the eventual consistency trade-off this forces.
    Command ModelRead ModelsProjectionsConsistency
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    Outbox Pattern
    The dual-write problem and how the transactional outbox solves it — writing to DB and publishing an event atomically.
    Dual WriteTransactional OutboxAtomicityAt-Least-Once
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    CDC
    Change Data Capture — reading the database write-ahead log to stream changes downstream without polling or dual writes.
    WAL TailingDebeziumLog MiningStreaming
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    Inbox + Outbox
    Combining inbox and outbox for end-to-end reliable delivery — idempotent consumers, deduplication, and the full event flow.
    Inbox PatternIdempotencyDeduplicationFull Flow
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