"""Even with fast NVMe drives and splitting the database into two halves (important data vs. ephemeral data that we could lose on a tmpfs), things got slower and slower. We knew the day would come. The file reached a peak size of 150MB and we were writing it as quickly as the disk I/O would let us. Ain’t that just peachy?"""

Uh, you compressed it first, right? because CPUs can compress data faster than disk I/O.