TransactionSync with Plaid Link - plaid

Question

I'm trying to render all the transactions for a given item after the completion of the Plaid Link process. I call my transaction sync endpoint in my onSuccess method after the exchange token process. However, the first call to the transaction sync endpoint never renders anything, but when I add another item through Link, the intial item's transactions renders and the current one doesn't. I'm wondering why I need to call the sync endpoint twice to actually sync it into my db. The first call I make returns this response:
{'added': [],
'has_more': False,
'modified': [],
'next_cursor': '',
'removed': [],
'request_id': 'qmJn54LkWHqo4kh'}
I'm assuming that the item isn't ready to sync transaction yet because the cursor is at its initial state, which is why the next time I link an item it syncs. If that is the case where should I call the sync enpoint, currently calling in the onSuccess method(also tried calling the endpoint of the "HANDOFF" event but same result). How would I know when the item's transactions are ready to sync.
This is my onSuccess method, I'm calling the sync endpoint after token exchange
const onSuccess = useCallback<PlaidLinkOnSuccess>((publicToken, metadata) => {
fetch('/item/public_token/exchange',{
method: 'POST',
headers:{
'Content-Type': 'application/json',
},
body: JSON.stringify({public_token: publicToken, id:uid, metadata:metadata})
})
.then((r) =>{
fetch('/transactions/sync', {
method: "POST",
headers: {
"Content-Type": "application/json",
},
body: JSON.stringify({uid: uid})
})
})
}, []);
This is method the sync endpoint hits
#app.route('/transactions/sync', methods=['POST'])
def transactions_sync():
id = request.json["uid"]
items = collection.find_one({"_id": ObjectId(id)},{"items":1})
print(items)
for item in items["items"]:
item_id = item["item_id"]
access_token=item["access_token"]
cursor = item['cursor']
added = []
modified = []
removed = []
has_more = True
while has_more:
transaction_request = TransactionsSyncRequest(
access_token=access_token,
cursor=cursor
)
print(transaction_request)
response = client.transactions_sync(transaction_request)
print(response)
added.extend(response["added"])
modified.extend(response["modified"])
removed.extend(response["removed"])
has_more = response["has_more"]
cursor = response["next_cursor"]
for add in added:
res = collection.update_one({"_id": ObjectId(id)},{"$push":{
"transactions":{
"account_id": add["account_id"],
"transaction_id":add["transaction_id"],
"amount":add["amount"],
"name": add["name"],
#"date": add["date"],
"category":add["category"]
}
}} )
print(cursor)
collection.update_one({
"_id":ObjectId(id),
"items.item_id": item_id
},{"$set":{
"items.$.cursor": cursor
}})
return "Success",200
I tried syncing the item's transactions in the onSuccess event for Plaid Link but it didn't sync into my database until I added another item through Link (essentially it took 2 calls to the endpoint to sync). I'm expecting to sync the transactions of the newly added item to my database so I can render on the frontend, with just one call the to sync enpoint

Answer 1

This sounds like a timing issue. From the /transactions/sync API reference:
"Note that for newly created Items, data may not be immediately available to /transactions/sync. Plaid begins preparing transactions data when the Item is created, but the process can take anywhere from a few seconds to several minutes to complete, depending on the number of transactions available."
If you call /transactions/sync immediately after the token exchange, it won't return any transactions, because they aren't available yet. By the time the new Item has been added, enough time has passed that the transactions have been loaded on the original Item.
After calling /transactions/sync for the first time on an Item, you will register the Item for the SYNC_UPDATES_AVAILABLE webhook, which you can then use to see when to call /transactions/sync. For more info, see the documentation for that webhook.