The Magpies earned a much-needed win by dispatching Gillingham 3-1 at Meadow Lane.
Derry, who took charge of the club a month ago, had only amassed a single point from his first four fixtures at the helm, and the former Queens Park Rangers midfielder, who turned 36 on Friday, has quipped that he has consequently aged since taking the job.
"It may have been my 36th birthday yesterday, but I look about 45 now," he told reporters.
"I've been waiting for that win since I've come through the door and I'm delighted it came under the circumstances that it did.
"I thought the whole team really delivered at a crucial time of the season. I thought at times we showed nervousness, but we scored at critical times."
County, who remain rooted to the foot of the League One table despite the win, travel to Colchester United in England's third tier next Saturday.