[SalesForce] Is there performance degradation when using Lightning components within an aura:iteration tag

Looking into aura framework source code you can see this warning is thrown when framework is doing it's own garbage collection.

If a single not-rendered component is destroyed, then framework will show you a warning. Commit message says it's been implemented to stop memory leakage.

Framework executes this cleanup after each update to the DOM.

This would be MUCH faster to do in your Apex controller than it would be to do in your lightning controller. The reason this is taking so long is because your iteration will look something like this:

// Outer loop
For(Account a:accounts){

    // Inner Nested Loop 1    
    // Loop through all of the accounts
    // to get related contacts (account.contacts)

    For(Contact c:contacts){ 
        //Add each related contact from the current account's query results  
        Contacts.add(Contacts.LastName);

        // Inner Nested Loop 2
        // loop through products for each Account Contact

        For(Product p:Products){
           OptionValue.add(p.Name);
        {

    }
}

To do the above, you go through every related contact that was returned for the Account to pull them out. Because you want them separated, you might have been better off to do that in the controller. I see no relationship between Product and Account.Contact. This is what seems to be killing your performance. You rebuild the select options repeatedly for each contact. If you created it once, then copied it to each contact that in itself would be more efficient.

Using a design where one component called another might be helpful in this context. If you could separate building the select options from the accounts & contacts you'd presumably find that very helpful towards performance.

Additionally, if you don't need to go back to the server for more products, you can use "setStorable" for any non-mutable functions that contain data which won't change (I doubt your products change and if your list of them doesn't, then this would be helpful to you). As a caution, do not use promises with storable actions!