Handling successful payment processing but database update failure

Question

I am trying to implement a stripe checkout process in one of my express.js routes. To do this, I have:

• Official Node.js Stripe module
• Official client-side Stripe module
• A json logger I use to log things like javascript errors, incoming requests and responses from external services like stripe, mongodb, etc…
• An Order model defined using mongoose - a MongoDB ODM

My steps are as follows:

Client:

1. Submit order details which include a stripe payment token

Server:

1. Create an unpaid order and save to database (order.status is created)
2. Use stripe client to charge user's credit/debit card
3. Update order and save to database (order.status is accepted or failed depending on response from Stripe)

Question: If payment is successful after step 2 but an error occurs updating the order in step 3 (due to database server error, outage or similar), what are some appropriate ways to handle this failure scenario and potentially recover from it?

Answer 1

With payment systems, you always need a consolidation process (hourly, daily, monthly) based on sane accounting principles that will check that every money flow is matched.

In your case, I suggest that every external async call logs the sent parameters and the received response. If you do not have a response within a certain time, you know that something has gone wrong on the external system (Stripe, in your case) or on the way back from the external system (you mention a database failure on your side)

Basically, for each async "transaction" that you spawn, you know when you start it and have to decide of a reasonable amount of time before it ends. Thus you have an expected_end_ts in the database.

If you have not received an answer after expected_end_ts, you know that something is wrong. Then you could ask for the status to Stripe or another PSP. Hopefully the API will give you a sane answer as to whether the payment went through or not.

Also note that you should add a step between 1. and 2 : re-read the database. You want to make sure that every payment request you make is really in the database, stored exactly as you are going to send it.