Planning a Worldwide Network: Edge Locations, Backbone Links, Routing and Resilience
Company: Citrix
Role: Product Manager
Category: System Design
Difficulty: medium
Interview Round: Other
You are a product manager at Citrix. Explain how you would design a global network infrastructure: the locations, links and routing that connect users and sites across continents. Cover what the network must do, its main building blocks and design choices, and how you would judge whether the design is working.
```hint Requirements before topology
Where you place sites and how you connect them depend on what traffic the network carries and how sensitive that traffic is to delay and outages. Settle those requirements before choosing locations, routing methods or vendors.
```
### Clarifying Questions
- Whose traffic does the network carry: connections from customers' users to a cloud service we operate, such as remote app and desktop sessions; links among a company's own offices and data centers; or both?
- Where are users concentrated, and roughly how many simultaneous connections and how much bandwidth should the first version support?
- What availability, latency and data-residency requirements apply, and do any customers work in regulated industries?
- Are we free to build our own backbone, or should the design rely on public cloud providers, carriers and the public internet?
### What a Strong Answer Covers
- Requirements and success measures derived from the traffic the network carries, such as responsiveness for interactive sessions, availability, capacity and compliance.
- A topology of regions, edge locations and backbone links, plus the routing that sends each user to a healthy nearby location.
- Resilience and security: redundancy, failover, capacity headroom, encryption, DDoS protection and identity-based access.
- Build-versus-buy and cost trade-offs, with a phased rollout.
- Monitoring of both network health and the experience customers actually get.
### Follow-up Questions
- A whole cloud region goes offline during its busiest hours. What do users experience, and how does the network recover?
- A large customer requires that its traffic and data never leave one country. What changes in the design?
- How would you decide where to add the next edge location?
Overview: A technical product question from a Citrix product manager interview about designing a global network infrastructure. It tests turning traffic, latency, availability and data-residency requirements into a topology of edge locations, backbone links and routing, along with resilience, security, monitoring and build-versus-buy trade-offs.