What should be used trigger or Transaction?

  1. Is triggers free with mongodb atlas?
  2. If yes, what are the pricing scenerio and is there some proper docs / course to learn the basics?
  3. What should we prefer incase we want to modify, multiple documents. For ex- I want to update wallet balance whenever a new order is added. We should use Transaction or triggers?

Hi – Triggers are priced separately from Atlas based on consumption but have a generous free tier (more info). For Triggers vs. Transactions it depends on the relationship you want between the data, should the be updated together (ex. if an order/balance cannot be updated together then neither happens – Transactions) or updated sequentially (ex. after adding an order update balances and run any other operations but allow the updates to happen separately – Triggers).