SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a31dc4ba4d63253db740ddb60f3225314e04a8a025cd72219633a886d7eead3' 
  AND token = 'm5aNfBiEPj4erNFyTyXu42bejrUxUofxk+sFCTfgsh0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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