SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3509bc4080ec5a70d8e425b8c9db0a61a0febf69b793fd2773df9841aa64241' 
  AND token = 'cOIbGkAzEf1I71lo+Zy1zWWx7Y5uOv+QqTBxCq12wH8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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