Work out multi region cost instantly with clear inputs, formula shown and shareable results.
Multi-region cost is not simply regions times single-region cost, because some components — a global control plane, CI, monitoring, shared tooling — stay in one place. The addition that catches people out is inter-region data transfer, which grows with replication volume and can become a significant line on a chatty architecture.
Multi-region cost
replicated = single-region cost x (1 - shared share); total = replicated x regions + shared + inter-region transfer
It depends whether the business genuinely requires surviving a regional failure. Most availability incidents are application bugs, which multi-region deployment does not fix and may complicate.
Data consistency. Compute is easy to replicate; deciding what happens to writes during a partition is the genuinely difficult design problem.