It really depends on what it was and how complex it is. For an automatic grant (e.g., attending the same school as an older sibling in a CES, continuing COSA to upper elementary, avoiding mandatory dual language) it's usually resolved quickly, sometimes before the end of the school year. For more complicated cases, it can take most of the summer.

Our youngest had 2 automatic COSAs in elementary school that were resolved within weeks of the April deadline.

We did a COSA for middle school last year and got an first-level rejection (that automatically goes to second-level review) at the end of June, then an approval near the end of July. When we called at the beginning of June, they said they were still processing COSAs from the current school year and hadn't even looked at requests for the next school year.

The cosa deadline was beginning of April

Especially on a COSA. They think you are scamming

For anything MCPS it will take twice as long as they say and you will have to nag and nag to get a definitive answer

Submitted my application 3 weeks ago and have yet to hear back. How long does it take to hear back?