SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39a221fb0074e7b908d4a273fb520814400a53c087f105337ede6055afd81789' 
  AND token = 'TS9UxwFLhdXqGhNmhlIcBpcZqF+zxQpKyEtfUDpd1Dg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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