SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '99dfa23b4991a473118215bbae8e208370f75912107b5a8fde91a366eff9dd80' 
  AND token = 'eTeVuiqCcn2N1lbbAnW03tDWKtj48az/S6cruU9bxSU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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