High-frequency trading (HFT) firms rely on colocated servers to minimise latency when sending orders to exchanges. However, leasing cross-connects and maintaining multiple links across the globe can be costly. Firms must carefully balance trade-offs between latency, bandwidth, and financial cost when designing their network. This project formalises the network design problem as a combinatorial optimisation task: selecting which cross-connects to lease and routing expected order flows to maximise total expected profit, while respecting latency and bandwidth constraints.