SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8cb9aa0d49f851bea705892b27875cfc575def3453aa428c450c271769db3abc' 
  AND token = '5YnpHGwwbmyYnCXMtQ/yLWHWlI08vQRFKZRh5ntxmrA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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