Never pay SDRs for meetings booked
Pay SDRs on meetings booked and meetings double while closed-won falls. The plan pays for what it says, so write it on the number you want moved.

Priya owns a 25-person software company (a composite, built from plans I've seen), and in January she signed a new SDR comp plan. In March every SDR was over target for the first time, and she pinned the leaderboard in the team channel. Two weeks later her AEs asked for a meeting about the meetings.
Say she had moved 60% of SDR bonus onto meetings booked in January. By March, meetings had doubled. By month seven, closed-won traced to those meetings had fallen by roughly forty percent. The previous plan paid on opportunities created, and people called it too lagging for monthly comp, so the new one paid on the cleaner, faster, more visible number. Cleaner and faster is how a comp plan hides its blast radius.
SDRs are paid to book meetings, so they booked meetings. That many of them were with prospects who were not evaluating, were the wrong profile, or could not sign anything sat outside the reward function. The reps were not careless. They read the incentive Priya signed and answered it precisely.
The bill has two lines. The first is cash. Say she had four SDRs on a $2,000 monthly bonus target, so the meetings share was $1,200 each, $4,800 a month across the team. At that rate, January to July is $33,600 paid on a number that had stopped predicting revenue. The second line is the AE calendar: every meeting with someone who can't buy is an hour an AE didn't spend on someone who can, which is where the forty percent went.
Point the plan at the number the company wants moved. For SDRs that is usually meetings held, weighted by whether the AE later qualifies them. Pure meeting count rewards noise. Pure closed-won lags too far for a monthly check. The blend, meetings this month times a quality factor that settles when the AE marks the opportunity real, costs more to administer and buys the right behavior. Any CRM, HubSpot or Salesforce, can hold that qualification field; the hard part is that the AE, not the SDR, sets it, and the owner pays the bonus off it. The same logic runs through any incentive you attach to people, which is why accountability has to sit on the outcome, not the activity.
Most teams reach for the simpler metric because it's easier to explain and easier to pay out. The simpler metric is also the one that buys the wrong behavior. The bill arrives two quarters later, in the pipeline that looked full and closed nothing.
A comp plan is a sentence the company writes and the team obeys word for word. Read yours and ask what it pays for. That is what you will get, every month, on payroll.