A self-tuning write throttle for batch Postgres jobs (opens in new tab)

I have a background job that writes a lot of rows. It chunks a big import into batches and upserts each batch into Postgres. On its own that’s fine. The problem is that it doesn’t run on its own: the same database is serving live traffic and a handful of other workers at the same time. When my import goes full tilt, everyone else feels it.