SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4c1ea5a7120e2c815d50573f1a74ffe56b550d810190b9c837285451f5b3736c' 
  AND token = 'pLqMMeZi6/5vjfShNcaHYcHo59Ck2SYsh6euexbHP5s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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