SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3db1678fc39a12022c75212f2145b8ccdc195223f51ced36d8bd71a924892beb' 
  AND token = '5YIevrZV1qNTqJeIygWA9TiB6mwYj7DgfXq2cpaS4ko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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