HTTP status code
HTTP status code: 502 Bad Gateway
What does 502 Bad Gateway mean in HTTP?
The server was acting as a gateway or proxy and received an invalid response from the server behind it.
Risk warning: CFDs and spread bets are complex instruments and come with a high risk of losing money rapidly due to leverage. You can lose money on these products, and each provider publishes its own loss figure under FCA rules. You should consider whether you understand how they work and whether you can afford to take the high risk of losing your money. Automated and API trading can amplify losses through bugs, connectivity failures and runaway orders.
What it means in trading API work
The machine that answered is a front door, and the service behind it gave a reply that made no sense. It is often brief. For a request that places, changes or cancels an order, the outcome is unknown, not failed.
This part is this site's own explanation, written for people learning to call a trading API. It is not part of the source cited above and it describes no particular broker.
What should I do about 502 Bad Gateway?
Wait and retry reads with growing gaps. For an order request, read open orders and positions before sending it again. Check the provider's status page if it lasts.
This page is an independent explanation in plain words. The definition itself is in the source it was read from, which is the authority if the two ever differ.