A technical guide to the tradeoffs and implementation patterns for active-active database architectures across regions, including conflict resolution strategies.
Choosing a consistency model
Strong consistency across regions requires synchronous replication, which adds meaningful write latency proportional to inter-region network distance — most active-active designs accept eventual consistency for the majority of data and reserve strong consistency for a small set of genuinely conflict-sensitive operations.
Conflict resolution strategies
Last-write-wins is simple but can silently lose data; CRDTs (conflict-free replicated data types) avoid this for compatible data structures; and application-level conflict resolution (versioning plus merge logic) is often necessary for anything more complex than simple counters or sets.
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