SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3476b02d039b0b43e553bbb7738095621887b7a98ebca060b33586447d475579' 
  AND token = 'fHR42Nu33otpKZ9X0UoyQpNFjaoAt7aWOj2Ww3+poiw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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