Fullstack system for event planning with offline mobile sync and multi-client architecture.
Strassable is a fullstack planning system built for the Eurometropole of Strasbourg around a web map editor, a NestJS API, and an offline-capable mobile field app.
Three-client system:
Web map editor for event preparation
Backend API for domain orchestration
Offline mobile app for field execution
Key mechanics:
QR-based transfer sessions
Local-first mobile storage with SQLite
Offline cartography with tiles and search
Clients
3 coordinated apps
Sync model
QR transfer sessions
Map support
Local tiles + search
Field mode
Offline mobile storage
Local maps and mobile SQLite storage had to remain useful while sync timing and routing constraints stayed explicit.
Web, API, and mobile needed clear contracts so each client could own a different slice of the workflow.
Routes, safety points, equipment, and timeline states had to stay readable on the same map surface.
Strassable combines a web map editor, local cartography services, QR-based transfer sessions, and an offline mobile field client.
City Ops
Event supervision and preparation
Map Editor
Projects, routes, teams, safety points
Transfer API
Domain orchestration and transfer endpoints
Field App
Offline mobile client for teams
Local Maps
MBTiles and local address search
Project DB
Projects, planning, equipment, photos
QR Bridge
Temporary sync session between clients
Field Data
Treated points, photos, team feedback
City Ops
Event supervision and preparation
Map Editor
Projects, routes, teams, safety points
Transfer API
Domain orchestration and transfer endpoints
Field App
Offline mobile client for teams
Local Maps
MBTiles and local address search
Project DB
Projects, planning, equipment, photos
QR Bridge
Temporary sync session between clients
Field Data
Treated points, photos, team feedback
Web editor owns preparation: routes, teams, safety points, and timeline review
NestJS API keeps project domains and transfer workflows centralized
Local map services keep tiles and address search available without network access
QR sessions create controlled import and return flows between clients
The mobile app works from SQLite data during field execution
The three surfaces that matter most: preparation, field execution, and transfer.
Web map editor
Preparation workspace for routes, teams, safety equipment, timeline review, and operational supervision.
Mobile field app
Imported projects stay usable on site through local storage and a field-oriented map view.
QR transfer
Temporary sessions make import and return flows explicit instead of hiding sync behind a permanent connection.
The split follows the real workflow: prepare, orchestrate, execute.
The web editor prepares the event, the API owns domain and transfer rules, and the mobile app executes from imported local data.
The QR bridge is deliberate: it creates a temporary sync context that fits field operations better than a permanently connected thin client.
Strong architecture, with honest boundaries around unfinished edges.
The offline story is strong for tiles, search, and mobile storage, while some navigation behavior still depends on external routing services.
The project is valuable as a portfolio case because it shows multi-client architecture, offline constraints, QR sync, and product decisions under real constraints.