SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56f279753f9bc534c633d980e49a18e286688f1b9de43562f44af1029b50fba7' 
  AND token = 'Fmo8CQKwOThGze7GYnQa2GoFYIeGq+/K9DuNFL81rPs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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