Working on call center infrastructure for the last few years has taught me something most vendor pitches won't tell you. The architecture decisions that work fine for 30 agents fall apart somewhere between 100 and 200 agents. And nobody warns you about it until you're already there. This is a write-up of the actual technical decisions that matter when building VoIP call center solutions that hold up under real load. The 100-Agent Wall Most teams pick their VoIP call center solution based on feature checkboxes. The demo looks great. The pricing seems reasonable. They go live with 30 agents and everything's fine for months. Then the team grows. Around the 100-agent mark, things start getting weird. Calls drop intermittently during peak hours. Reports take forever to generate. Database queries that ran in milliseconds now take seconds. Reps complain that the dashboard is "slow" without being able to point to a specific issue. What's actually happening is that the architecture wasn't built for that load.…