A software engineer writing about AWS, Python, and building things on the web.https://andrewgilliland.dev/https://andrewgilliland.dev/articles/authorizer-lambdas-with-cognito-and-api-gateway/https://andrewgilliland.dev/articles/authorizer-lambdas-with-cognito-and-api-gateway/Cognito can tell you who a user is, but it cannot answer what they are allowed to do. An authorizer Lambda gives you one place to evaluate permissions before a request reaches your backend, with Cognito for identity and a separate permission source for authorization.Mon, 29 Jun 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/asset-cdn-with-s3-cloudfront-route53-acm-and-cdk/https://andrewgilliland.dev/articles/asset-cdn-with-s3-cloudfront-route53-acm-and-cdk/Build a fast asset pipeline with a private S3 origin, CloudFront caching, custom DNS, and HTTPS certificates using AWS CDK.Mon, 22 Jun 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/real-time-image-optimization-with-lambda-on-s3-upload/https://andrewgilliland.dev/articles/real-time-image-optimization-with-lambda-on-s3-upload/Automatically optimize images the moment they're uploaded to S3 using Lambda functions triggered by S3 events. Perfect for user-generated content and dynamic workflows.Mon, 22 Jun 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-sqs/https://andrewgilliland.dev/articles/intro-to-sqs/SQS is AWS's managed message queue service. Messages go in, consumers pull them out, and the queue handles everything in between. Here's what it is, when to use it, and how to implement the common patterns.Mon, 15 Jun 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/what-is-an-agent-harness/https://andrewgilliland.dev/articles/what-is-an-agent-harness/The model is just token prediction. An agent harness is everything else - the loop, the tools, the memory, and the safety controls that make a model actually useful.Mon, 08 Jun 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/how-to-build-a-permission-gate-extension-with-pi/https://andrewgilliland.dev/articles/how-to-build-a-permission-gate-extension-with-pi/Pi is a minimal, extensible coding agent. This article walks through building a permission gate extension that intercepts dangerous bash commands before they run.Sun, 07 Jun 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/hosting-tanstack-start-on-aws/https://andrewgilliland.dev/articles/hosting-tanstack-start-on-aws/How to deploy a TanStack Start SSR app to AWS using Lambda or ECS Fargate, wired together with CloudFront, S3, and CDK.Thu, 04 Jun 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/autonomous-test-generation-with-playwright-and-claude/https://andrewgilliland.dev/articles/autonomous-test-generation-with-playwright-and-claude/How to build an AI agent that crawls your site, observes each page, and writes Playwright spec files - without you authoring a single selector.Thu, 28 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/ai-powered-e2e-testing-with-playwright-and-claude/https://andrewgilliland.dev/articles/ai-powered-e2e-testing-with-playwright-and-claude/How to use Claude's API alongside Playwright to write semantic smoke tests that reason about page state instead of matching brittle selectors.Wed, 27 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-machine-learning-with-scikit-learn/https://andrewgilliland.dev/articles/intro-to-machine-learning-with-scikit-learn/Machine learning sounds intimidating, but scikit-learn makes it approachable. Here's how to train your first model in Python.Fri, 22 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/reducing-alert-noise-with-cloudwatch-composite-alarms/https://andrewgilliland.dev/articles/reducing-alert-noise-with-cloudwatch-composite-alarms/When your database goes down, every service that depends on it starts throwing errors. Composite alarms let you express alarm logic so you get one page per root cause, not one per symptom.Mon, 18 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/cleaning-and-exploring-data-with-python/https://andrewgilliland.dev/articles/cleaning-and-exploring-data-with-python/Real data is messy. Here's how to handle missing values, fix types, and explore datasets before doing anything useful with them.Fri, 15 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/building-data-pipelines-with-step-functions-and-lambda/https://andrewgilliland.dev/articles/building-data-pipelines-with-step-functions-and-lambda/When one Lambda isn't enough, Step Functions lets you orchestrate multi-step workflows with retries, error handling, and a full execution history built in.Tue, 12 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/lambda-authorizers/https://andrewgilliland.dev/articles/lambda-authorizers/The Events API is built and fast. Now POST /events and DELETE /events/{id} need auth. Lambda authorizers let you validate any token format from any issuer before a request ever reaches your handler.Sun, 10 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/structuring-a-lambda-api-for-performance/https://andrewgilliland.dev/articles/structuring-a-lambda-api-for-performance/The architecture decisions that make a Lambda-backed API fast - per-route function layout, lean handlers, per-function dependencies, ARM64, and CDK patterns that compound into short cold starts.Thu, 07 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/lambda-cold-starts/https://andrewgilliland.dev/articles/lambda-cold-starts/What happens during a Lambda cold start, how to measure it with X-Ray and CloudWatch Logs Insights, and how to reduce it with lean packages, init code patterns, and provisioned concurrency.Wed, 06 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/lambda-with-rds-proxy/https://andrewgilliland.dev/articles/lambda-with-rds-proxy/Why Lambda exhausts RDS connection limits under load, and how to fix it with RDS Proxy - including CDK setup, IAM auth, and connection reuse.Tue, 05 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/e2e-testing-with-playwright/https://andrewgilliland.dev/articles/e2e-testing-with-playwright/How to add end-to-end tests to a React app with Playwright, including checkout flow testing for e-commerce, and run them automatically on every pull request.Mon, 04 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/getting-started-with-pandas-for-data-science/https://andrewgilliland.dev/articles/getting-started-with-pandas-for-data-science/Pandas is Python's answer to working with tabular data. Here's a practical intro for developers who've never touched a DataFrame.Sun, 03 May 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/the-working-dad-workout-program/https://andrewgilliland.dev/articles/the-working-dad-workout-program/Finding time to work out with a full-time job and kids is hard. Here's the program that actually works.Thu, 30 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/environment-variables-secrets-and-ssm-parameter-store/https://andrewgilliland.dev/articles/environment-variables-secrets-and-ssm-parameter-store/Hardcoded config doesn't scale and hardcoded secrets are a security incident waiting to happen. Here's how to manage environment variables, secrets, and configuration for Lambda functions on AWS - from local development to production.Wed, 29 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/rds-access-with-ssm-port-forwarding/https://andrewgilliland.dev/articles/rds-access-with-ssm-port-forwarding/RDS in a private subnet doesn't need a bastion host or an open port 22. AWS Systems Manager port forwarding creates an encrypted tunnel from your laptop to a private endpoint - no public IP, no SSH key management required. Here's how to set it up with CDK.Mon, 27 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-ec2/https://andrewgilliland.dev/articles/intro-to-ec2/EC2 is AWS's virtual machine service - rent compute capacity in the cloud, pay by the hour. Here's what it is, when to use it over serverless options, the configuration knobs that matter, and how to provision it with CDK.Sun, 26 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intersection-observer-api/https://andrewgilliland.dev/articles/intersection-observer-api/The Intersection Observer API lets you detect when elements enter or leave the viewport - without scroll event listeners. Here's what it solves, how it works, and real patterns you can use today.Fri, 24 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-sns/https://andrewgilliland.dev/articles/intro-to-sns/SNS is AWS's pub/sub messaging service. One message in, many subscribers notified. Here's what it is, when to use it, and how to implement the common patterns.Thu, 23 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/cloudwatch-alarms-with-sns-and-slack/https://andrewgilliland.dev/articles/cloudwatch-alarms-with-sns-and-slack/CloudWatch Alarms don't notify anyone on their own. Here's how to wire them to SNS for email alerts and a Lambda function for Slack notifications.Wed, 22 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/monitoring-and-observability-on-aws/https://andrewgilliland.dev/articles/monitoring-and-observability-on-aws/Your code is deployed. Now make sure it stays healthy. Here's how to monitor Lambda functions with CloudWatch.Tue, 21 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/continuous-deployment-to-aws-with-github-actions-and-oidc/https://andrewgilliland.dev/articles/continuous-deployment-to-aws-with-github-actions-and-oidc/How to set up keyless, secure continuous deployment to AWS using GitHub Actions and OIDC - and why it beats AWS-native CI/CD tools for most teams.Thu, 16 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/python-type-hints-for-typescript-developers/https://andrewgilliland.dev/articles/python-type-hints-for-typescript-developers/You already think in types from TypeScript. Here's how to bring that mindset to Python with type hints, mypy, and Pydantic.Wed, 15 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/python-for-javascript-developers/https://andrewgilliland.dev/articles/python-for-javascript-developers/A side-by-side look at Python through the lens of JavaScript. If you know JS, you're closer to writing Python than you think.Tue, 14 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-aws-cdk/https://andrewgilliland.dev/articles/intro-to-aws-cdk/AWS CDK lets you define cloud infrastructure with real code instead of YAML. Here's how to get started with TypeScript.Mon, 13 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/your-first-aws-lambda-function-with-python/https://andrewgilliland.dev/articles/your-first-aws-lambda-function-with-python/Write, test, and deploy a Python Lambda function from scratch. No prior AWS experience needed.Sun, 12 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/infrastructure-as-code-cdk-vs-cloudformation/https://andrewgilliland.dev/articles/infrastructure-as-code-cdk-vs-cloudformation/CloudFormation uses YAML. CDK uses TypeScript. Here's when to use each and why CDK feels like a superpower.Sat, 11 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/building-a-rest-api-with-api-gateway-and-lambda/https://andrewgilliland.dev/articles/building-a-rest-api-with-api-gateway-and-lambda/Wire up API Gateway to Lambda functions and build a serverless REST API using Python and CDK.Tue, 07 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-dynamodb-for-python-developers/https://andrewgilliland.dev/articles/intro-to-dynamodb-for-python-developers/DynamoDB is the serverless database that pairs naturally with Lambda. Here's how to use it from Python.Tue, 07 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-github-actions/https://andrewgilliland.dev/articles/intro-to-github-actions/GitHub Actions is CI/CD built directly into GitHub. No external service to configure. Push code, merge a PR, cut a release - automation runs. Here's what it is, how workflows are structured, and real examples for the most common use cases.Mon, 06 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-docker-for-python-and-lambda/https://andrewgilliland.dev/articles/intro-to-docker-for-python-and-lambda/When zip files aren't enough, container images let you package anything for Lambda. Here's how to use Docker with Python.Sat, 04 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/python-sqlalchemy-aurora-migrations/https://andrewgilliland.dev/articles/python-sqlalchemy-aurora-migrations/You have an Aurora database running in AWS. Now you need to get your schema into it. Here's how to define your data models with SQLAlchemy, manage migrations with Alembic, and run them against Aurora - step by step.Wed, 01 Apr 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-s3/https://andrewgilliland.dev/articles/intro-to-s3/S3 is AWS's object storage service - store any file at any scale. Here's what it is, what it's built for, what it isn't, what it works with, and how to deploy it with CDK.Tue, 31 Mar 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/aws-glossary/https://andrewgilliland.dev/articles/aws-glossary/Definitions for the AWS services and concepts covered across the architecture articles on this site. VPCs, subnets, Lambda, API Gateway, EventBridge, SQS, Step Functions, RDS, Aurora, security groups, and everything in between.Sun, 29 Mar 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/intro-to-aws-lambda/https://andrewgilliland.dev/articles/intro-to-aws-lambda/Lambda is AWS's serverless compute service - run code without managing servers, pay only for what you use. Here's what it is, why it's worth knowing, when to reach for something else, and how to deploy it with CDK.Sun, 29 Mar 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/aws-rds-vs-aurora/https://andrewgilliland.dev/articles/aws-rds-vs-aurora/Both RDS and Aurora are managed relational databases, but they're built differently. Here's how to choose between them for a new project.Fri, 27 Mar 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/three-tier-architecture-on-aws/https://andrewgilliland.dev/articles/three-tier-architecture-on-aws/The classic three-tier architecture - presentation, application, and data layers inside a VPC - is the foundation of most production AWS deployments. Here's how it works, how subnets and security groups enforce it, and how to deploy it with CDK.Wed, 25 Mar 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/amazon-eventbridge/https://andrewgilliland.dev/articles/amazon-eventbridge/EventBridge is a serverless event bus that connects your applications with data from AWS services, SaaS apps, and custom sources. Learn what it is, the problems it solves, and how to implement it with CDK.Tue, 24 Mar 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/ci-cd-for-lambda-functions-with-github-actions/https://andrewgilliland.dev/articles/ci-cd-for-lambda-functions-with-github-actions/Stop running cdk deploy from your laptop. Set up a GitHub Actions pipeline to test and deploy your Lambda functions automatically.Mon, 23 Mar 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/uv-is-the-npm-of-python/https://andrewgilliland.dev/articles/uv-is-the-npm-of-python/If you're a JavaScript developer curious about Python, uv makes the tooling feel familiar. Here's how it maps to what you already know.Sun, 22 Mar 2026 00:00:00 GMThttps://andrewgilliland.dev/articles/data-visualization-with-d3/https://andrewgilliland.dev/articles/data-visualization-with-d3/Build interactive data visualizations using D3.js and React. See live examples of bar charts, donut charts, and line charts you can embed directly in your content.Tue, 24 Jun 2025 00:00:00 GMThttps://andrewgilliland.dev/articles/typescript-tips/https://andrewgilliland.dev/articles/typescript-tips/A handful of TypeScript patterns that have made my code more expressive, safer, and easier to refactor.Fri, 20 Jun 2025 00:00:00 GMThttps://andrewgilliland.dev/articles/why-i-use-tailwind/https://andrewgilliland.dev/articles/why-i-use-tailwind/Tailwind CSS changed how I think about styling. Here's why utility-first CSS has become my default approach.Tue, 04 Mar 2025 00:00:00 GMThttps://andrewgilliland.dev/articles/getting-started-with-astro/https://andrewgilliland.dev/articles/getting-started-with-astro/Astro is a modern web framework that lets you build fast, content-focused websites using your favorite UI components.Wed, 15 Jan 2025 00:00:00 GMT