Ka Lun Chan
Section301

Case study

WhereGlobal communications platform
RoleCo-Founder & CTO

From one data center to three continents

Users on three continents got the same fast, reliable service, with no big-bang migration.

Cloud & infrastructure / Software architecture / Engineering leadership

Problem

The platform started in one data center. As the user base grew past 400,000 across North America, Europe and Asia, distance itself became the problem: every session from the far side of an ocean paid for it in latency and quality.

Constraints

  • A small engineering team that also owned operations
  • No downtime window: users were active in every time zone
  • Real-time traffic, which a static CDN cannot hide
  • Startup budget: capacity had to follow revenue

Architecture & approach

Keep one architecture and run it in three places. Each region carries the full web and application tier, users resolve to the nearest healthy region, and data replicates back to a primary. Regions went live one at a time, so every step could be rolled back.

Fig. 301-2Geo-routed regional deployment Critical path

Key decisions

How should distant users reach the platform? 301-3.1

  • RejectedStay in one region and add a CDNCheap, but only static assets get faster. Real-time traffic still crosses the ocean.
  • ChosenGeo-routed full regional stacksEvery region serves the whole application. Users resolve to the nearest one.
  • RejectedSeparate product instance per marketFast locally, but it forks the codebase and the team.

How should the migration run? 301-3.2

  • RejectedCut over everything at onceShort project, unbounded blast radius.
  • ChosenRegion by region, reversible at each stepSlower, but each step is observable and can be rolled back.

Outcome

  1. 400k+ users served across North America, Europe and Asia
  2. Lower network latency and better quality for distant users
  3. Multimillion-dollar growth and a successful acquisition

Technology

Multi-tier web & mobile application, Data center design, Cloud regions (NA / EU / Asia), Geo-location DNS routing, Data replication

Lessons & tradeoffs

  • Latency is a product feature. Users feel geography before they notice any new feature.
  • Designing the first data center carefully made leaving it easier. Clean tiers moved as units.