Well, you probably want to decrease response time but otherwise yes. It's good to give objective metrics for your accomplishments. Also helps to frame the interview. "I see here you improved the response time of an API by 15%, tell me about that".
"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)
Your second line is improvement for sure. But it follows the same basic advice to give numbers