SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fab4cb8f9978851f7da414db004589eb33f9567cc996b274008901895df8527' 
  AND token = 'y3jWWCzvcUHqv9eBIcqxEYIWJmucmDXVGFYrpp90cxg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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