Serverless Bedrock APIs

Lambda + API Gateway is a strong default for many Bedrock workloads: scalable, managed, and easy to secure. The shape is simple - but several LLM-specific details separate a working demo from a solid service.

The Reference Pipeline

API Gateway (auth, throttle, validate)
  → Lambda (contract validation → prompt assembly → Bedrock call → shaping)
      → bedrock-runtime.converse(...)
  → telemetry (traceId, tokens, latency, guardrail action)

A Handler Shaped for Production

const { BedrockRuntimeClient, ConverseCommand } = require("@aws-sdk/client-bedrock-runtime");
const client = new BedrockRuntimeClient({});   // init OUTSIDE handler - reused across warm invocations

exports.handler = async (event) => {
  const body = validate(JSON.parse(event.body));       // 1. contract first
  if (!body.ok) return { statusCode: 400, body: body.error };

  const out = await client.send(new ConverseCommand({
    modelId: process.env.MODEL_ID,                      // 2. config, not hardcode
    messages: [{ role: "user", content: [{ text: body.prompt }] }],
    inferenceConfig: { maxTokens: 512 },
  }));

  log({ traceId: event.requestContext.requestId,        // 3. telemetry every call
        usage: out.usage, stop: out.stopReason });
  return { statusCode: 200, body: JSON.stringify(out.output.message) };
};

LLM-Specific Lambda Settings

• Validate request contracts at the API boundary - schemas on API Gateway plus in-handler checks.
• Attach an execution role with narrow Bedrock permissions (pinned model ARNs - see the IAM module).
• Emit trace IDs for every invocation and propagate them into tool calls.