SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f43a1e30c0c2aafc55a14edd3e76da57cdf0ba154f8c20024fc4609b873d5793' 
  AND token = 'eUYHnBw2SWVbaHV1JegebD1pmjv90gDpSxDS+p2kxcY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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