Glossary

Cross-AZ latency

Cross-AZ latency is the round-trip time for network traffic between different availability zones within a single cloud region. Most cloud providers keep intra-region, cross-AZ latency below about 2 ms RTT, but it adds up on the hot path. Cross-AZ data transfer is often billed per GB, making it both a latency and a cost concern for high-throughput systems.

Formula: Typical AWS same-region cross-AZ RTT about 0.3–1.5 ms; with Kafka RF=3 across zones, produce with acks=all includes cross-AZ replication RTT.

Last updated: March 2026