Serverless Archives

How to invalidate Cognito-issued JWT tokens

API Gateway, AWS, Cognito, Lambda, Serverless

The ability to invalidate a user’s session with immediate effect is a common enterprise requirement.

However, this goes against how token-based authentication is designed to work. JWT tokens are stateless and are typically short-lived (for security reasons) but can be refreshed with refresh tokens.

So, is it possible to invalidate Cognito-issued JWT tokens?

The short answer is no.

The long answer is yes, you can achieve this effect with some work and some performance overhead.

How? Well, come in and find out!

Biggest re:Invent 2024 serverless announcements

AWS, Serverless

So that’s it for this year’s re:Invent. Werner delivered his usual insightful keynote and shared some key lessons in dealing with complexity and warning signs to look out for. As Werner said, the number of moving parts is not a good measure of complexity on its own. And that’s something so many people get wrong …

Biggest re:Invent 2024 serverless announcements Read More »

Biggest pre:Invent 2024 serverless announcements

AWS, CloudFormation, Cognito, DynamoDB, Lambda, Serverless, Step Functions

DynamoDB cuts on-demand price by 50% Announcement DynamoDB has reduced on-demand pricing by 50% and global tables by up to 67%. Amazing! Lambda SnapStart is now available for Python and .Net Announcement Previously, SnapStart was only available for Java. It makes sense to add support for .Net. But why Python and not Node.js? I guess …

Biggest pre:Invent 2024 serverless announcements Read More »

Here is one of the most misunderstood aspects of AWS Lambda

AWS, Lambda, Serverless

One of the most misunderstood aspects of Lambda is how throttling applies to async invocations. Or rather, how it doesn’t!

The TL;DR is that you will never experience throttling when you invoke a function asynchronously.

It also means that despite SNS and EventBridge having longer retry periods than Lambda’s internal queue, these have no practical impact in the case of Lambda throttling.

Read the full post to understand why.

Should “serverless” just mean “function-as-a-service”?

AWS, Serverless

Gregor Hohpe said something that has me mulling over for some time now. Essentially, he asked, “Should we narrow the definition of serverless to mean just function-as-a-service (FaaS)?” “Serviceful” For context, I’m firmly in the “serverless means serviceful” camp: a) Serverless is a mindset: To leverage managed services to deal with undifferentiated heavy lifting so …

Should “serverless” just mean “function-as-a-service”? Read More »

What’s the best way to do fan-out/fan-in serverlessly in 2024?

AWS, Serverless, Step Functions

Back in 2018, I shared several ways to implement fan-out/fan-in with Lambda. A lot has changed since, so let’s explore the solution space in 2024.

Remember, what’s “best” depends on your context. I will do my best to outline the trade-offs you should consider.

I’m sorry, but the way you adopt serverless is wrong

AWS, Serverless

Here is the biggest mistake many teams make when they try to adopt serverless and why they ultimately fail.

Don’t make the same mistake.

AppSync’s new async Lambda resolver is great news for GenAI apps

AppSync, AWS, Serverless

AppSync now supports invoking Lambda resolvers asynchronously. This simplifies a common challenge in GenAI applications where we had to hand off the call to the LLM to a background function so we can stream the LLM response back to the caller.

How to handle execution timeouts in AWS Step Functions

AWS, Serverless, Step Functions

Step Functions lets you set a timeout on both Task states and the whole execution. By default, an execution can run for a year if TimeoutSeconds is not configured. To a user, the execution would appear as “stuck”. Which is why AWS best practices recommend using timeouts to avoid such scenarios. But once you have configured a timeout for the execution, it’s then important to consider what happens when you experience a timeout.

In this post, let’s explore 3 ways you can handle an execution timeout and use a Lambda function to perform automated remediation (e.g. applying rollbacks).

How to apply the TDD mindset to serverless

AWS, Serverless, Testing

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.