Neither my banks nor Venmo offered a way to Programmatically access my transactions in real time. 

The API for my financial accounts was hiding in plain sight. All of my credit cards, debit cards, and even Venmo account had the option to turn on email purchase notifications. 

I laid out the architecture diagram of how my spending tracking application would work:

1. Incoming emails with purchase notifications would be forwarded to a backend service. 
2. The transaction description and dollar amount would be parsed and assigned a category. 
3. The record would then be uploaded to a database.