SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ab8f2a38031e211f8bab06382b747bd1460d55e6ba892c0fa413f3378eb38721' 
  AND token = 'OYpYhOxm4gK+wQbb0sbgjAnc6MyXjHVe+PWHEkJVwzg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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