Ah, I just recommended simple AMQP (packed BSON <128k messages) for RabbitMQ with client x509 cert GUID access as secure "middleware" to link all the legacy systems together. The addition of a strict sanitization producer/consumer process bound to each cpu core handles a sliding window idempotent operation handler. Or, people can corrupt their own data if they really try for a finite period, but the system eventually becomes consistent.

Notably, it is possible to rebuild or move the entire infrastructure by issuing a signed resend-logs-to-new-consumer request to clients or servers.

If you start with a dumpster fire at a dried fish factory, than 3 week solutions that last 6+ years under load look pretty nice in retrospect. Your boss is probably contemplating why most Erlang/Elixir people don't work for clown wages. =3