Scaling up: Brokerage infrastructure and managing liquidity across venues

We're reaching a point where our current broker setup is starting to show its limitations, particularly around aggregating liquidity from multiple providers efficiently without introducing excessive latency. The fee structures, while competitive at lower volumes, become less so when we're talking about significantly increased flow and tighter spreads. How are others managing this at scale? Specifically interested in solutions for intelligent order routing and effective netting across different clearing venues to minimize overall transaction costs and optimize our capital requirements. Are there platforms that genuinely excel at this without becoming a huge integration headache?