A combination of different technologies makes it possible to have an eye on the rates of the most important precious metals. Users can define their own boundaries for notifications, push messages inform if the rates hit the boundaries on the way up or down.
The technical aspect of that was challenging. Data that changes in seconds, different resolutions of data that can be queried and all of that has to respond in milliseconds. The frontend has to work cross platform on iOS and Android while displaying the data neatly.
The combination of CouchDB, InfluxDb, Redis and Node.js is responsible for the frictionless operation of the backend: CouchDB provides the application data, InfluxDB the exchange rates and Redis handles the alerts.
A couple of Node.js microservices are orchestrating the components and handling decisions. For the extra performance in times of high load, Varnish provides the perfect cache-layer.
With D3.js it's possible to visualize even ambitious data sets with the ease of web technology. As a key to this app, it was now possible to make it work cross-platform. Cordova enabled native App Store versions for iOS and Android.