A lean algorithm will comfortably execute every tick even in a busy market. Of course if it can't be processed before the next tick comes in, subsequent executions will run late, though we leave this up to the trader and hope to just provide the most performant execution environment we can.

We find no issues running scripts of reasonably high complexity. Of course if you have a particularly heavy algorithm it may be better suited to running at interval close.

With regard to legal position, you're absolutely right. While we're in beta you can connect to live broker accounts, though we are blocking order requests from actually being sent. We want to be water tight both technically and legally before we full launch with regulatory authorization, lifting this restriction and allowing real money to be risked.

As with brokers, we just want to support as many as we can. FXCM were a natural first choice for integration as they have excellent support for API solutions and have the most fully featured FIX implementation we've come across. Of course it's up to the trader to establish if any conflict of interest scenario exists between themselves and the broker.