Connections on paid plans now refresh every hour instead of twice a day. Median sync time dropped from 11 seconds to under 3, and the slowest 1% of syncs went from over 90 seconds to 14.

Most of the gain came from replacing our sequential fetch with a parallel one — we were requesting accounts one at a time from each institution, which meant a household with six accounts waited for six round trips. We also stopped re-requesting transaction history we already had, which cut the data we pull on a typical sync by around 80%.

The practical difference is that a transaction you make at lunch is in Cassis before you get back to your desk, and the balance on your dashboard is one you can actually act on.