SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3be3b72c54eb2c22ada65c90736c83de37208ec4e3aa9ed7de75b68681c541a4' 
  AND token = 'JN6DUuu8eUPhH9HmM+zH8DC/s06PSllmxxG0lttSHCE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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