plaid

How To Get/Compute Starting Balance From Plaid

Using Plaid in a consumer facing app. When someone first links a bank account I only want to get the last 5 days worth of transactions (if any)... and then I want to compute what the "starting balance" was just before those transactions. (Please just trust me that I need that "starting balance" for my app!)

My idea here is to get the current balance and then subtract off the transactions for the last 5 days.

The docs effectively say that the /transactions/get API is deprecated - and I should use /transactions/sync. That's fine - but /transactions/sync doesn't provide the current account balance.

I could call /accounts/balance/get, but that causes a balance refresh that might give me a newer balance that includes transactions that have come in after I've been through /transactions/sync.

/accounts/get is another option - and seems to return the "cached" balance that is probably the correct balance that goes with the transactions that just came through from sync... but there is no guarantee. It's definitely possible that Plaid could have updated their cached balance to one that includes transactions beyond what I just got from sync.

Basically: as far as I can tell, there is not a solution that uses sync and guarantees a current balance that perfectly matches. Why in the heck doesn't sync return THE current balance that goes with the transactions that just came through?

So now - I feel like I'm going to use /transactions/get... because it WILL return the current balance and all of the transactions that went into the calculation of that balance. Unfortunately, this may return a huge amount of data - and I'll just have to throw it all away other than the last 5 days.

My plan is this:

  1. Link account
  2. Receive INITIAL webhook
  3. Call /transactions/get
  4. Get all of the transactions, only keep the last 5 days worth
  5. Pull the current balance out of the response
  6. Subtract off the last 5 days worth of transactions to compute the "starting balance" before those.
  7. Call /transactions/sync to tell Plaid that I want to use the sync API going forward.
  8. Read all of the transactions from sync, throw away all transactions other than the last 5 days worth.
  9. Verify that the last 5 days worth of transactions are the same (modify any that have changed, delete any that went away, add any new ones)
  10. Carry on using sync going forward.

Am I crazy? Is there a better way?!?

No errors - just unclear on the best way to proceed.

Solution

  • In step 4, why not just get the last 5 days of transactions? /transactions/get allows you to specify the date range you want. Note /transactions/get isn’t going away any time soon (it will probably never go away) we just don’t recommend it as it has a number of usability problems that /transactions/sync solves. If you find it better for your use case, it’s fine to use. P.S. While it is theoretically possible that /accounts/get could return a different balance than /transactions/sync, if called immediately after, the odds of this happening should be so low as to be effectively zero.

    EDIT TO ADD: The safe way to do it is: if you call /transactions/sync, then call /accounts/get, and then call /transactions/sync again and receive no new transactions, you can safely assume that the balance returned by /accounts/get is up-to-date with /transactions/sync. Alternatively, you can listen for webhooks and can safely assume that the balances are the same until you receive a SYNC_UPDATES_AVAILABLE webhook.