Technical Overview

This page gives a brief overview of the Metro Retro architecture and system requirements.

Introduction

Metro Retro is a dynamic, real-time application providing users with a rich interactive environment to work collaboratively. It is primarily deployed into a virtual private cloud operated by Deqo Software Ltd and provided in the form of Software as a Service.

This article describes the architecture of Metro Retro. See our Security and Privacy Policy pages for more information on our security and data protection practices.

Logical Topology

Metro Retro is exposed to customers as a single page web application. Behind this, there are a number of services working in synergy to provide a working service. From a logical perspective (ignoring hardware), these are:

Service	Product / Provider	Role
Web Gateway	Caddy	Acts as reverse proxy and load balancer.
Content Delivery Network	BunnyCDN	Provides edge cache for static assets & SPA build files.
App Server	NodeJS Application	Application API (HTTP based) and Auth/Login UI.
Podopolis	Elixir Application	Socket server that enables the real time collaboration functionality.
Main Database	Postgres	Stores all system data except for board contents.
Object Database	MongoDB	Stores board contents.
Cache	Redis	Provides a cache and short term storage solution.
Message Queue	Rabbit MQ	Enables inter-service communication between components.
File Store	S3 Compatible Storage	Stores static assets & user uploaded data.
App Worker	NodeJS Application	Background job processor for various system tasks/functionality.
Snapper	NodeJS Application	Generates board preview images via Puppeteer.

The diagram below shows the logical topology layout including the data transfer routes. Blue lines are one way transfers, purple lines are bi-directional transfers.

Physical Topology

Cloud Deployment

Within the main cloud deployment, we utilize Digital Ocean with the following:

• Ubuntu VMs for App Server, App Worker, Snapper, Podopolis, Rabbit MQ, Redis & Caddy

• Digital Ocean Managed Postgres & MongoDB instances

• Digital Ocean Spaces (S3 Compatible Storage)

• Bunny CDN as the external CDN provider

Each component runs directly on a dedicated VM of a size applicable for the current system load.