We have all new hires take surveys at 14, 45, and 90 days.  They cover everything from onboarding, to their mentor experience, to training.  I just implemented a survey at 90 days from the leader perspective so we'll be able to compare it to their recent hire.  We use survey monkey for most surveys and our admin sets them up and pulls the data for us.

We'll also survey around big events, but most small one off L&D training, etc the sample size is so small surveys don't get us any actionable data.

I've done shorter polls within Microsoft Teams.  So the other day there was a specific group and I wanted to know what type of resource would be most helpful.  For example 1:1 mentoring, mentoring circles, guest speakers, etc.  I put a poll in the channel for that group and got quick results on how to best support that group.