SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '35003371641e5511da26998717fa238df1f5b8f1fa38809783ddf09cce728c7a' 
  AND token = 'y+8Z+FW6mxhbi7NK7AlDEDcmASUvjRVzMizPgyJI9oQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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