aws-lambda

A reference guide to common problems when deploying .NET applications as AWS Lambda functions, including network access and logging. AWS Lambda is Amazon's service for running code without managing servers.

In plain words
What is it for?
Use it when configuring Lambda functions in a private network, checking access to Amazon S3 or Secrets Manager, investigating startup delays, or choosing reliable .NET logging.
Why use it?
It helps explain failures that can look like application or SDK bugs, such as timeouts caused by missing network routes or incomplete logs.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/axgord/claude-workflow/aws-lambda
Any agent
npx skills add AxGord/claude-workflow --skill aws-lambda
Clone the repo
git clone --depth 1 https://github.com/AxGord/claude-workflow

Made for: Claude Code, Codex.

Per session 11 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,043 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00011 $0.01043
Opus 5 $0.00005 $0.00522
Sonnet 5 $0.00002 $0.00209
Haiku 4.5 $0.00001 $0.00104

Measured 2d ago against content hash 03e1cd2fb72e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

aws-lambda scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

templates/skills/aws-lambda/SKILL.md · 45 lines

How it starts

The opening of the file, as written. The whole thing — 45 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AWS Lambda + .NET Gotchas

VPC Networking

  • ENIs are shared since the Hyperplane rework (2019) — one ENI per subnet + security-group combo, created when the function is created or its VPC config changes, NOT per concurrent execution. Scale-up does not consume a subnet IP per instance, so subnet IP exhaustion from Lambda scaling is largely a pre-2019 concern.
  • ENI provisioning takes up to ~90s at function create / VPC-config change; the function reports LastUpdateStatus: InProgress until done. (The old per-invoke ENI cold-start penalty is gone.)
  • S3/Secrets Manager calls timeout silently (not connection refused) when Lambda is in VPC without NAT/VPC Endpoint. Easy to misdiagnose as SDK bug.

Logging

  • Console.Error.WriteLine() IS captured by CloudWatch on the managed .NET runtime (Lambda redirects the process's stdout/stderr) — but entries lack the request-id prefix and multi-line output splits into separate events. Output genuinely disappears only in narrower cases: writes during a crashed INIT (process torn down before flush) or a custom-runtime bootstrap that doesn't forward stderr. Prefer ILambdaContext.Logger.LogLine() in handler code or ILogger in the ASP.NET pipeline.
  • Missing logs:CreateLogGroup permission = logs silently lost. Log group created lazily on first invoke. No permission = no log group = nowhere to write = no error visible anywhere.

ASP.NET Core in Lambda

  • UseHttpsRedirection() hangs Lambda. No Kestrel HTTPS port. Middleware hangs trying to discover one (aws-lambda-dotnet #1543; discussion #1424 reports the same shape — handler completes but the response never reaches the runtime — as warm-invoke middleware timeouts on a custom runtime). Only enable in Development.
  • Response > 6MB fails the invoke — no clean HTTP 413. 6MB is the synchronous INVOKE-phase request/response payload limit (nothing to do with INIT). APIGatewayHttpApiV2ProxyFunction surfaces it as a runtime-client error for that invocation, so the caller sees a generic 500-style failure instead of a 413.

Read the full file on GitHub · 45 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 45 lines · 11 tokens per session scan A 03e1cd2fb72e

Subscribe to this mod's changes

aws-lambda is a skill published in the GitHub repository AxGord/claude-workflow (5 stars, last pushed 1mo ago), licensed MIT. It adds 11 tokens to every session and 1,043 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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