The 270-Second Rule: How Anthropic's Cache TTL Should Shape Your Multi-Agent Architecture

When you build a multi-agent orchestration loop, you'll eventually face a question nobody talks about: how fast should the orchestrator tick? We ran ours too fast for two weeks before we noticed the problem. Then we ran it too slow. The right answer turned out to be a specific number - 270 seconds - derived from one Anthropic infrastructure detail that most people don't know exists. The cache TTL you're probably ignoring Anthropic's prompt caching has a 5-minute TTL. After 5 minutes, the cache entry expires and the next request pays full input-token cost to re-process the context.