SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '475b8abc8c0fee850b4d6641982764bbd02aa9812a1c1e2c7836e78171eca289' 
  AND token = 'Mu4WjDtnLv7YnRJ2T/ES3Z+JrhHBMCRjghkesBRGhnE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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