18 karma · joined December 11, 2019
Turning a noisy GPS trace into a "you rode this segment, in this direction, at this time" wass a real problem, so I used an HMM map-matcher — Newson-Krumm / Viterbi, the same family OSRM and Valhalla use. Candidate road edges are the hidden states, the emission probability is a Gaussian on how far each fix sits from an edge, and the transition probability punishes disagreement between along-road distance and straight-line distance. It's direction-aware (forward, reverse, and out-and-back all mint separately) and this was shockingly difficult to implement.
The thing that actually makes it fun is that the racing happens during the ride. When you hit a segment you're chasing, you get a live +/- against a ghost of the current holder. Originally this came in as a static ghost divided evenly by the total time, however, that is not accurate so now we use an actual reconstruction of their splits, so if they went out hot and you're clawing it back on the second half, you see exactly that, in real time. Instead of one all-time board that goes hopeless, crowns live on rolling windows (today / this week / this month / all-time), so there's almost always a bar that's genuinely in reach. That's a direct fix for the "my PR is unreachable on 19 of 20 rides" problem every mature Strava segment eventually has. And we added something called Keeps & Trials which, think Pokemon Gym, where time degrades over time on short circuits to allow you to race them over and over and over.
Map coverage is demand-driven. I was tempted to just map everything all at once, but I didn't want to just blow cash on hosting for the world when it isn't needed. So rather than pre-ingest everything, now when a rider shows up somewhere new, the area gets tiled with H3 hexes (Uber's hex grid, res 5, ~100 sq mi a cell) and only the uncovered hexes trigger a road-graph build from OSM/Overpass. The hex index is the dedup key, so the rule is literally "never ask the API for a place we already have," and the map fills in exactly where people ride and nowhere they don't.
Sensors are BLE GATT against the standard profiles — FTMS for smart trainers, Cycling Power (including pedal balance and the whole Zwift controller matrix: Click, Play, Ride, Sterzo), heart rate, speed/cadence. On the phone that's CoreBluetooth; on the desktop/world side there's a native Rust BLE stack so the same sim can run off a real trainer. Although, I don't own a power meter to validate that in the real world so if anyone wants to do that....
WASM - 374KB Raw || 148KB gzipped
JS and HTML - 31KB Raw || 8KB gzipped
Total - 404KB Raw || TLDR; 156KB for the end user
I need to add some love into those two areas for sure. As well as Safari and edge cases, etc. If anyone wants to contribute...
Regarding regulators and obligation -- in any of these relationships the bank is ultimately responsible/liable for any AML/TFL, money, etc... irregularities. A BaaS provider can effectively do everything wrong to the point its underlying bank is shut down, and switch to a different partner bank.
The majority of the banking industry is built on Cobol. Open Banking is the only real path forward. The issue of the US vs EU open-banking is the number of community banks.
The, unfortunate, most reliable banks from a technology/data perspective are ones that are large enough to be loathsome to deal with. Think JP Morgan, BoA.
Even banks of that size, Comerica, have had massive ledgering issues recently, so they are not immune.
Some reputable players in the BaaS industry are Unit, JP Morgan, Jack Henry, Moov(Massive plug for them), VGS (works with Visa and MC btw). If your neo-bank works with them, I would trust my money there. I do trust my money with one of those partners.
Evolve is an otherwise obscure bank chartered in Arkansas but headquartered in Tennessee (a little sketchy) that has over-leveraged itself. This is why it was hit with a Cease and Desist from the FDIC. The C&D also probably contributed to them becoming a target for LockBit.
Evolve is also the underlying bank for Stripe Treasury, although to my knowledge, their have been no new partnerships with them. I have heard the number 2 thrown around. Of note, Shopify is the main person for whom this was built and uses this.
Consequently if you have submitted KYC/KYB information for Shopify, Mercury, Yotta, Dave, any other past Synapse partners, or some Modern Treasury partners your data was breached. This seems to be the primary information shared along with account and routing numbers. This becomes problematic especially as part of the check involves external account and routing numbers along with SSN of any UBOs.
Fintechs do not partner with small banks because of debit card fees but because of Dodd Frank regulations (primarily).