13.5Memory Configuration Testing

For AWS Lambda, CPU is proportional to memory. More memory means more CPU, which can reduce execution time enough to offset the higher per-ms cost:

# lambda_memory_optimizer.py
"""
Test a Lambda function across memory configurations to find the cost-optimal setting.
More memory = faster execution but higher per-ms cost.
The sweet spot minimizes (execution_time_ms * memory_mb * cost_per_gb_ms).
"""
import boto3
import time
import json

lambda_client = boto3.client('lambda')

def benchmark_memory_config(function_name: str, payload: dict, memory_sizes: list[int]) -> list:
    results = []

    for memory_mb in memory_sizes:
        # Update function memory
        lambda_client.update_function_configuration(
            FunctionName=function_name,
            MemorySize=memory_mb,
        )
        time.sleep(10)  # wait for update to propagate

        # Run 10 invocations and collect timings
        durations = []
        for _ in range(10):
            start = time.perf_counter()
            response = lambda_client.invoke(
                FunctionName=function_name,
                Payload=json.dumps(payload),
            )
            wall_time = (time.perf_counter() - start) * 1000
            billed_ms = json.loads(response['Payload'].read())
            durations.append(wall_time)

        avg_duration = sum(durations) / len(durations)
        # AWS pricing: $0.0000166667 per GB-second
        cost_per_invocation = (memory_mb / 1024) * (avg_duration / 1000) * 0.0000166667

        results.append({
            "memory_mb": memory_mb,
            "avg_duration_ms": round(avg_duration, 1),
            "p99_duration_ms": round(sorted(durations)[8], 1),
            "cost_per_invocation": f"${cost_per_invocation:.8f}",
        })

    return results

# Example usage
results = benchmark_memory_config(
    "my-function",
    {"key": "test-payload"},
    [128, 256, 512, 1024, 2048, 3072],
)
for r in results:
    print(f"{r['memory_mb']}MB: {r['avg_duration_ms']}ms avg, {r['cost_per_invocation']}/invocation")