SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '323971aff8e0e7177d581f81c9b538181962d3fbbf49908a9d0472721091f635' 
  AND token = 'NknYzGhlWFGUCX6jlqrMzf7Zj0JIp4I//aED1Nt/zQM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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