SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '290511226759fd945b2c64ea98e5c049db4c165636007a7335d91309954c374a' 
  AND token = 'gkbBo1CjBbimKAGjDKZkeW0KW9ma4cyqegh/U1Le6oE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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