A nightly job that ran until morning

Enterprise Java, a 4.2-hour batch, and a coverage number that did not match the risk of changing it.

2021 — 2022

4.2 h → 38 min

Nightly batch

41% → 78%

Test coverage

The situation

Core backend services sat under high-volume commerce and logistics. One nightly batch was still running into the morning. Tests covered less than half the domain, which made the obvious query work feel unsafe.

The work

I maintained and extended the Java services on that path.
I tuned the critical SQL and stored procedures. The largest win was the nightly job.
I raised automated test coverage across the assigned service domains so the next change was cheaper.