Thursday, 12th March 2026
Inside an AgentCore microVM — Ports, Cold Starts, and the Sidecar Pattern
When you deploy an agent on Amazon Bedrock AgentCore Runtime, your Docker container runs inside a Firecracker microVM. But what actually happens inside that microVM? Here’s the complete picture:
[... 1,408 words]What Actually Happens When You Call invoke_agent_runtime()
You call invoke_agent_runtime(). Your agent responds 3 seconds later. But what actually happened in those 3 seconds? There’s an entire orchestration layer that you never see: sidecars, health checks, microVM boot sequences. Here’s the full picture.
The 95% Rule: Why Your Agent Is Slow and How to Prove It
Your agent takes 5 seconds to respond. Where did those 5 seconds go? AgentCore gives you 6 observability layers, 30 hidden metrics, and a debugging decision tree. But you have to know where to look. Here’s everything you can’t see by just reading the code.
[... 2,831 words]I Ran 100 Parallel Tool Calls on AgentCore — The microVM Didn’t Break, But the LLM Did
What happens when you fire 100 tool calls in parallel inside a single AgentCore microVM? Does the microVM crash? Does it run out of memory? Does the thread pool explode? I deployed an agent with 100 tools to Amazon Bedrock AgentCore Runtime and ran a scaling test from 5 to 100 parallel tool calls. Here’s exactly what happened.
[... 2,716 words]