[aksx]

Even if your current employer let's you talk about specific numbers, without context they don't tell the recruiter anything.

"The API latency was 10 seconds, now it's 8.5 seconds."

or

"I reduced the p99.9 latency from 1 sec to 400ms" (by removing input validation)

[treis]

If the best thing you did was take an API from 10 to 8.5 it's probably best to tell the recruiter as little as possible.

Your second line is improvement for sure. But it follows the same basic advice to give numbers