The current flow for ApiFeatureUsage is that usage logs are collected via logstash, which has an output to the cirrus elasticsearch clusters. This causes multiple issues:
- synchronous flow: if the cirrus cluster is down for maintenance (or crashed) logstash pipeline will stall (see T176335)
- strong coupling: logstash and the cirrus cluster need to run compatible versions of logstash / elasticsearch, which can be problematic during upgrades
We should rework this data flow, probably using kafka, which would take care of both those issues.