Horizon endpoint /accounts?asset=<USDC> getting 503's

[jcx120]

What version are you using?

Horizon SDF 2.21

What did you do?

503 error after running curl https://horizon.stellar.org/accounts/?asset=USDC%3AGA5ZSEJYB37JRC5AVCIA5MOP4RHTM335X2KGX3IHOJAPP5RE34K4KZVN

What did you expect to see?

a working response

What did you see instead?

503 error

More Context:

Assets such as USDC, AQUA will have unbounded accounts associated with them. This endpoint should only return the first 10 records with paging support but is timing out.

graphana metrics seems to indicate DB query timeout/potential saturation risk:
https://grafana.stellar-ops.com/d/vHv3RMNMz/horizon-dashboard-bartek?orgId=1&var-environment=prd&var-cluster=blue&var-network=pubnet&var-route=All&var-interval=5m&from=now-6h&to=now