SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ca2efd618c58e2bdb3f86e7606427fc099b401b4cb564235b3a3f5af75656673' 
  AND token = 'UwKZFM+jQSEOQXjhyB7WykHNXOUdQqktRS9PnWPS1OY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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