SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3abfffa97ac20bad9acd8125cd1071854dd49b4db3c59571256a1f6455c7de08' 
  AND token = '2bjWHpGV9bP2bkjJc5hRlsjlRvIS3zf2ryRVpvvcL3Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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