Programming Archives

How to apply the TDD mindset to serverless

Testing is an integral part of software development, and serverless is no different.

Test Driven Development, or TDD, is long regarded as a leading practice in software development. And yet, one of the most misunderstood parts of Test-Driven Development (TDD) is the “Driven” part of the name. It’s not just about “writing tests before you write the code”. If your tests do not inform and drive your API design, then you’re not really doing TDD.

In this post, let’s look at how we can apply the TDD mindset to serverless and use our tests to drive the design of our serverless application.

Here are four ways you can implement WebSockets using serverless

API Gateway, AppSync, AWS, IoT Core, Momento, Serverless, WebSocket

There are many ways you can implement WebSockets with serverless technologies nowadays.

In this post, let’s explore four options – API Gateway, AppSync, IoT Core and Momento Topics. We will look at how they work, their pricing model and compare them.

DynamoDB now supports cross-account access. But is that a good idea?

AWS, DynamoDB, Security

DynamoDB now supports resource-based policies, which simplified cross-account access to tables.

But just because you can, doesn’t mean you should!

Cross-account access to DynamoDB tables is almost always a smell. But as with everything, there are exceptions and edge cases. You should think carefully before you use resource-based policies to enable cross-account access to your DynamoDB tables.

In this post, let’s explore some legitimate use cases for cross-account access to DynamoDB tables.

When to use Step Functions vs. doing it all in a Lambda function

AWS, Lambda, Serverless, Step Functions

I’m a big fan of Step Functions, but it’s yet another AWS service you must learn and pay for.

It also introduces additional complexities. My application is harder to test; my business logic is split between configuration (ASL) and code; and I have new decision points, such as whether to use Express Workflows or Standard Workflows.

So it’s fair to ask, “Why should we even bother with Step Functions?”. Why not just do everything in code, inside a Lambda function?

Let’s break down the pros and cons and look at the trade-offs of each.

When to use API Gateway vs. Lambda Function URLs

API Gateway, AWS, Lambda, Serverless

“Lambdalith” is a monolithic approach to building serverless applications where a single Lambda function serves an entire API, instead of having one function per endpoint. It’s an increasingly popular approach and provides portability between Lambda and containers and lets you use familiar web frameworks.

Tools like the AWS Lambda Web Adapter have made this approach more accessible, and it also works well with Lambda Function URLs.

But don’t be too hasty to get rid of API Gateway just yet!

In this post, let’s look at the pros and cons of API Gateway vs. Lambda Function URLs, and let me explain why I still prefer API Gateway.

First impressions of the fastest JavaScript runtime for Lambda

AWS, Javascript, Lambda, Serverless

LLRT, the new Low Latency Runtime for JavaScript, is an experimental runtime for Lambda that promises 10x faster startup time!

In this post, let’s look at why it’s so damn fast, and what design choices it makes (and why they make sense in the context of Lambda).

What’s the best way to migrate Cognito users to a new user pool?

AWS, Cognito, Lambda, Serverless

The challenge with a Cognito User Pool migration is that the user password cannot be extracted from Cognito. This is a good thing. It shows that Cognito follows security best practices and does not store user passwords in plain text.

But it makes our lives more difficult during a Cognito User Pool migration.

In this post, let’s consider three approaches for migrating users to a new Cognito User Pool.

How to secure CI/CD pipelines without burning developer productivity to the ground

AWS, Security

When it comes to CI/CD roles, your instinct might be to lock them down to just what it needs. Because we all want to follow the principle of least privilege. But as you will see in this post, this comes with a hefty price in terms of developer productivity, and it’s not as secure as you might think.

So instead, I prefer a more holistic approach when it comes to securing CI/CD pipelines, involving account boundaries, SCPs, ABAC and the use of permissive roles. Come in and find out how.

First impressions of CloudFormation’s IaC generator and CDK migrate

AWS, CDK, CloudFormation, SAM

AWS just announced the CloudFormation IaC Generator and added a CDK migrate command. These make it easier for you to manage manually created resources with Infrastructure as Code.

This is my first impressions of it – what worked, what didn’t and where the gaps are.

How to reprocess Lambda dead-letter queue messages on-demand

AWS, Serverless

Imagine this. You have followed AWS best practices and set up a dead-letter queue (DLQ) or an OnFailure destination for every async Lambda function.

A message arrives in your DLQ. You are alerted right away because you have alarms on all of your DLQs.

You investigate the problem and determine that it was temporary and the message should be re-processed.

But now what?