Yeah i see, but with all these coins, when we see the bitcoin's blockchain it's more than 200Gb, ethereum a bit less and all others coins it's a lot of Tb and the bandwidth for sync all these blockchains!! 

An other question came to my mind, these exchanges need to download all the blockchain of all the coins they use?

in intersango, what i understand that they use cronjob for first check every minutes if there are news deposits or withdrawals requests and after process to them if there are?

Hi,

First sorry if it's a newbie question!
I'm try to understand how this platforms work, specially the part for deposit/withdrawal.

I read about bitcoin daemon, so i understand how they generate account/address for users but where i misunderstand it's about the notifications of deposit and withdrawal and the usage of the balance information in database, they use wallet notify for that?

If yes, i read that wallet notify is call when: - a transaction arrive / - a transaction had her first validation / - and when a transaction is send

my questions are how they can use database for balance management, how that update of db work? If they use in add a cold storage system how that work?  

Because in my head that means:
      1 the user send bitcoin to his address:   first call wallet notify and maybe update of DB (or other script but in this case how and when they update their DB)
      2 the transaction had her first validation:   second call wallet notify who call herself the same script that config in
      3 the coin are move for cold storage or other: third call wallet notify who call herself the same script that config in

someone can explain me how that works please?    

Thanks