Rebuilding indexes very slow, production client

We are experiencing a pretty critical issue with a client. This is a client with a pretty large db. At some point, EventStore crashed. I am not sure the specific error they received that crashed EventStore.

However, when they try to restart Eventstore, they are in a situation where it is rebuilding inexes.

We are using version

To be clear, they left the database rebuilding indexes for weeks without it finishing.

I do have a log message:

[PID:04904:017 2021.03.13 00:00:51.416 DEBUG IndexCommitter ] ReadIndex Rebuilding: processed 2734447060 records (48.2%).

The machine has 32gb ram, but memory is pegged at 99% while this is going on.