SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '54ecdb45862f58fe4556b5092dbaee646542b4aa34a8d5fa387da3c900bb096c' 
  AND token = '/3bVqxnlDMv1qs/DYV0NBN5J68zyxqZ9Z3tu1/aP2Sc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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