Order rate limits and the EA that modifies too often

[Shadow Trader]

An EA that updates a trailing stop on every tick can send hundreds of modification requests per minute. Brokers watch this. Many have limits on the number of requests per second or per minute, and exceeding them leads to errors, delayed processing or account warnings.

In MT4, error 141, "too many requests", is the platform's way of saying the limit was hit. Some servers don't send that error but just ignore or delay requests.

The effect on a scalper is that the stop doesn't move when it should. The EA believes it has modified the order, and the server hasn't. A trade may then hit the old stop level.

Brokers also impose limits on total orders per day. For EAs that place and cancel pending orders constantly, the limit can be reached within hours, and further orders are rejected.

Good practice in EA design is to modify only when the change exceeds a minimum step, say 0.5 pips, and to limit the frequency to once per second or less. Logging every request and response shows whether any were rejected.

Checking the broker's terms for numerical limits tells the rules. Some state exact thresholds, like 100 requests per minute. Others use vague terms.

An EA that works well on demo, where limits are rarely enforced, can fail on a live account for this reason.

Has a request limit ever interfered with an EA, and how was it discovered?