Size a message queue from arrival rate, retention and message size.
Queue storage multiplies by the replication factor, so a three-times replicated topic needs three times the raw volume. Retention is usually the largest and most adjustable term. Log-based brokers retain messages after consumption to allow replay, which makes retention a storage decision rather than a delivery one.
Message Queue Size
Storage = rate × retention seconds × compressed message size × replication factor
Storage = rate × retention seconds × compressed message size × replication factor Queue storage multiplies by the replication factor, so a three-times replicated topic needs three times the raw volume. Retention is usually the largest and most adjustable term.
Log-based brokers retain messages after consumption to allow replay, which makes retention a storage decision rather than a delivery one.
This calculator takes 5 inputs: Messages per second, Average message size, Retention period, Replication factor, Compression saving. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.