I've been working on and off on Finny. I think I've already spent enough time overall though and have failed to deliver a working product in its current state. So I'm going to rip out the Plaid integration and build directly on YNAB's API. I've been a user of YNAB for the past half decade. This will circumvent my largest issue. This was inspired by YNAB's new Reflect feature.  

YNAB has already done all the work of setting up most of the ETL pipelines and have hit all the edge cases of integrating with multiple providers, including Apple Card. I just have to stand on their shoulders to perform my calculations.

Yes there will eventually be some ETL still because I want to be a good steward of YNAB's request limits, but I can circumvent the truly annoying part of my work: categorizing transactions, specifically transfer transactions. Transfer transactions were affecting my inflow and outflows, and I couldn't figure out a viable solution without doing a lot of work to balance out net transfers. The core number underpinning my calculations is having an accurate running expense number. YNAB offers that because I use YNAB and bucket all my transactions.   

Ultimately all I want is a retirement calculator for myself. I entertained the idea of spinning Finny into some real product, but I'm happy to keep it small. 

Perhaps if it's good enough, it'll be something YNAB adds to their app or purchase from me.

Dennis