SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '591936720d4ec21844699de70de23a2f56974d3f33588a594b561ff5f200576c' 
  AND token = '49x91oPSTKkgJim+HFg0s/+A2EDvp+CxY8L93RWXuMs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}