Snapjack
A multiplayer bankroll manager for at-home poker games. iOS native, web companion, event-sourced ledger, and a multiplayer Glicko-2 rating pipeline — built end to end by one engineer.
The shape of it
Snapjack is what I wanted to exist when I started running a regular home game: a single place to track buy-ins, settle the cash, and watch a real rating emerge over a year of Tuesday nights. The product is small. The engineering behind it isn't.
Underneath the iOS and web apps sits a shared TypeScript monorepo — types, Zod schemas, and a typed API client that both surfaces import directly. The server is a Next.js app with roughly 200 API routes, a third of which run the admin tools that keep games clean and ratings honest.
The core is an append-only ledger. Every chip movement is an event; balances, statistics, and ratings are projections. That decision shaped almost everything else.
The high-level picture
Solo-built · Live on iOS + Web · ≈ 200 API routes · Custom multiplayer analytics
Client · native
iOSLive · App Store
iOSLive · App StoreExpo SDK 52React NativeNativeWindReanimatedSkiaRevenueCat
Client · webWebLive · snapjack.app
WebLive · snapjack.appNext.js 14React 18TailwindRadix UID3 + Recharts
Client · adminAdminInternal · /admin
AdminInternal · /adminNext.js 14React 18TailwindRechartsD3
{ shared client + model }
@snapjack/typesDomain types — the model
Axios
React Query
Zod validates all requests
Next.js 14 API1Request Pipeline — cross-cutting concerns
Auth
- NextAuth · Apple + Google + Email
- JWT issuance + validation (jose)
- Guest → registered conversion
- MongoDB session adapter
Middleware
- Dual-layer route middleware
- Per-user rate limiting
- League-specific authorization
- Subscription gating
- Security headers
2Core Engines — services/
Gameevent-sourced lifecycle
Settlement7 sub-services
AnalyticsPlayerStats projection
Notifymulti-channel gate
Leaguefeed · stats recalc
Adminoperator surface → own routes
3Route Groups — by domain
Public surfacesuser-facing
Identity & Social
Auth 8 · Users 10 · Invitations 9 · Friendships 7
Game Lifecycle
Games 23 · Poker 4 · Activity 1 · Stats 4 · PlayerStats 1
Money
Settlements 19 · Transactions 6 · Subscription 2
Discovery & UX
Search 2 · Notifications 6 · Analytics 4 · Theme 1
System
Health 1 · Cron 1
Inbound Webhooks
RevenueCat 2
Restricted · Admin Portal67 routes
Operational Overrides
Settle overrides 5 · League ops 4 · Rating tuning 5
Visualizations & KPIs
Dashboards 18 · Retention · Churn · Conversion
Cleanup & Integrity
Debt-network 3 · Friendship 3 · Recalc jobs 5
User Management
Users 8 · Bans 3 · Roles 2
Bulk Operations
Import 4 · Preview 2 · Confirm 1
Inbound OAuthAuth Providers
Apple·Google·Email
Inbound webhook
RevenueCatsubscription events
RevenueCatsubscription eventsRead layer
Indexingprojections · query indexes
Indexingprojections · query indexes PlayerStats projection Game · Session indexes Compound queries
DataMongoDBMongoose · event log + projections
MongoDBMongoose · event log + projectionsNotification Center
pushExpo Server SDKmail
Mailgunalerts
Telegram
MailgunalertsTelegramClientsZod validates all requestsInboundNext.js 14 API
Client · nativeiOSLive · App Store
iOSLive · App StoreExpo SDK 52React NativeNativeWindReanimatedSkiaRevenueCat
Client · webWebLive · snapjack.app
WebLive · snapjack.appNext.js 14React 18TailwindRadix UID3 + Recharts
Client · adminAdminInternal · /admin
AdminInternal · /adminNext.js 14React 18TailwindRechartsD3
↓data hooks
{ shared client + model }
@snapjack/typesDomain types — the model
Zod validates all requestsInbound OAuthAuth Providers
Apple·Google·Email
Inbound webhookRevenueCatsubscription events
RevenueCatsubscription events↓posts to /api
Next.js 14 API1Request Pipeline — cross-cutting concerns
Auth
- NextAuth · Apple + Google + Email
- JWT issuance + validation (jose)
- Guest → registered conversion
- MongoDB session adapter
Middleware
- Dual-layer route middleware
- Per-user rate limiting
- League-specific authorization
- Subscription gating
- Security headers
2Core Engines — services/
Gameevent-sourced lifecycle
Settlement7 sub-services
AnalyticsPlayerStats projection
Notifymulti-channel gate
Leaguefeed · stats recalc
Adminoperator surface → own routes
3Route Groups — by domain
Public surfacesuser-facing
Identity & Social
Auth 8 · Users 10 · Invitations 9 · Friendships 7
Game Lifecycle
Games 23 · Poker 4 · Activity 1 · Stats 4 · PlayerStats 1
Money
Settlements 19 · Transactions 6 · Subscription 2
Discovery & UX
Search 2 · Notifications 6 · Analytics 4 · Theme 1
System
Health 1 · Cron 1
Inbound Webhooks
RevenueCat 2
Restricted · Admin Portal67 routes
Operational Overrides
Settle overrides 5 · League ops 4 · Rating tuning 5
Visualizations & KPIs
Dashboards 18 · Retention · Churn · Conversion
Cleanup & Integrity
Debt-network 3 · Friendship 3 · Recalc jobs 5
User Management
Users 8 · Bans 3 · Roles 2
Bulk Operations
Import 4 · Preview 2 · Confirm 1
2Every wire is Zod-validated. Shared schemas drive client ↔ server. Service-specific schemas guard external integrations.
↓queries
Read layerIndexingprojections · query indexes
Indexingprojections · query indexes PlayerStats projection Game · Session indexes Compound queries
↓Mongoose
DataMongoDBMongoose · event log + projections
MongoDBMongoose · event log + projectionsevents↓
Notification Center
pushExpo Server SDKmailMailgunalertsTelegram
MailgunalertsTelegram deployed surface shared code (compile-time only) external service inbound webhook outbound integration
The technical stack
Layer 01 · Surfaces
User-facing apps
Two surfaces, one product. Both speak the same shared types.
Distribution
Layer 02 · Client frameworks
The render layer
RN on iOS, Next on web. Identical patterns where possible.
Layer 03 · Shared monorepo
The contract
Turborepo + npm workspaces. The model only exists once.
Packages
@snapjack/types@snapjack/schemas@snapjack/api-client
Layer 04 · API
~200 routes
67 of them under /admin — analytics, settlement, moderation.
Routing & auth
Middleware & messaging
Dual-layer route middlewarePer-user rate limitingExpo Server SDK · PushMailgun.jsNodemailerTelegraf · Telegram bot
Layer 05 · Domain
The engine room
Where Snapjack stops being a CRUD app and starts being a poker app.
Models
GameUserTransactionSettlementPlayerStatsGameSessionFriends
Engines
Event-sourced game stateLedger-based settlementWelford online varianceSharpe ratioMax drawdown
Rating pipeline · Glicko-2
Per-game min-max profit normalization→ Exponential rank scoring→ Weighted combination→ Two-phi-split update
Layer 06 · Infrastructure
Where it runs
Boring, on purpose. Vercel + MongoDB + EAS.
Data flow · one request, end to end
- 01iOS / Web → import shared package → typed api-client call
- 02Hits a Next.js API route → validated by shared Zod schema
- 03Route queries MongoDB via Mongoose → returns typed response
- 04Auth: client → NextAuth → MongoDB adapter → JWT issued
- 05Subscriptions: iOS → RevenueCat → webhook → API → MongoDB
- 06Push: API → Expo Server SDK → user devices
Figure 02 · Six layers, one request — the model never leaves the type system.