Configuring Bedrock AgentCore Runtime V2 Agents with AWS Lambda Web Functions BFF and Cost Analysis

AgentCore Runtime V2 records P75 cold starts of 1.9–2.0 seconds via snapshot restoration, regardless of image size
In a 1 million requests per month scenario, Web Functions BFF costs 4.12 USD, which is approximately 49 times cheaper than Event Functions (200.20 USD)
Approximately 81% of total computing costs arise from idle memory, making the reduction of idleRuntimeSessionTimeout the core of cost optimization
Model token costs (approx. 4,938 USD) are approximately 4 times larger than computing costs (approx. 810–1,268 USD)

Architecture and Configuration

The streaming architecture consists of CloudFront, Web Functions BFF, AgentCore Runtime V2, and Amazon Bedrock
The BFF handles IAM signing, session mapping, input validation, and SSE heartbeat transmission
Operated in the Tokyo region; the Seoul region is used as the Tokyo region is employed because V2 is not supported in Seoul

Both Strands Agents and Claude Agent SDK show similar cold starts of approximately 2 seconds in V2
Time to first token is faster for Strands Agents (0.82–2.35 seconds) than for Claude Agent SDK (2.16–5.90 seconds)
Claude Agent SDK experiences latency due to subprocess startup and the transmission of long system prompts

Shortening the idle session timeout is the most effective for cost reduction
It is recommended to store user IDs and conversation IDs as keys in DynamoDB to prevent session ID guessing
Three-tier throttling management is required for Web Functions, AgentCore Runtime, and Bedrock models