SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a6a04c53016cc2717384ccf652531dad06b0984509597265fc837ebdbdaa0d60' 
  AND token = 'yDdhLqY3Hf9EJKejpvKlm1hDVZ+Ag4RJ2PJ12HmBMFQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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