Analysis of Amazon Bedrock AgentCore Runtime's microVM Isolation Principles and Selection Criteria

Details

AgentCore Runtime applies microVM isolation, showing lower system call overhead than gVisor (getppid 0.0407s) while maintaining performance similar to runc
Session creation latency has a median of 1.41s, which is faster than EKS Cold Start, and 200 sessions can be created concurrently within 2.6s without pre-provisioned capacity
Idle CPU is not billed; with 240s of idle time, the actual billed CPU is only 2.9s, making it advantageous for reducing interactive agent costs
microVMs are limited to a maximum of 2 vCPU, 8 GB memory, and 8 hours, making them unsuitable for GPUs or long-running tasks; for such workloads, using the Instances type (up to 14 days, GPU support) or EKS is recommended
Session idle determination is based on /ping responses; even during synchronous request processing, if the status is Healthy, the VM may be reclaimed according to timeouts, making retry logic implementation essential
The V2 snapshot restoration feature shortens initialization time from 11.63s to 2.56s, but since random numbers and tokens remain identical upon restoration, it cannot be used for session differentiation
Compared to direct EKS configuration, node management and pre-capacity adjustment are unnecessary, but developers bear application-level security responsibilities, such as session ID-user mapping and setting up least-privilege execution roles

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