Top 25 AWS Lambda Interview Questions And Answers in 2024

Editorial Team

AWS Lambda

Lambda is a priceless tool for developers and coders. This serverless computing service eliminates the need for server management or computing when running code. Instead, it runs code based on events such as update changes and automatically manages the needed computer resources. If you are currently looking for a Lambda-related job, you are in the right place. 

This article will look at some of the questions to expect in a Lambda interview so that you prepare in advance. We want to help you avoid any last-minute surprise that may throw you off, keeping you from getting the job you deserve. Let’s get started. 

1. What’s AWS Lambda, And How Many Languages Does It Support? 

AWS Lambda is a service offered by Amazon Web Services that allows serverless computing. It runs code based on different events and automatically manages the underlying computer resources. It also supports seven languages, that is, Python, PowerShell, Ruby, Go, js, Java, and C#

2. Do You Think Lambda Saves Time When It Comes To Coding? 

Yes. Lambda is a timesaver mainly because all the resources are stored in local server memory, making them easy to manage. It can also store data in its database directly without experiencing any performance issues. Lastly, Lambda comes with relatively simple testing techniques, such as integration testing, which can be made better by several vendors. 

3. Does AWS Lambda Come With Any Limitations? 

Despite being an innovative platform, Lambda has its shortcomings. First, it is unsuitable for long-running workloads, given that a function can run for a maximum of 15 minutes with a default timeout of 3 seconds. Also, each invocated Lambda function has a limited payload of 6MB and memory of below 3GB. Additionally, Lambda limits users to 1000 concurrent executions, which leads to a denial of service. Lastly, this debugging platform has monitoring and debugging limitations which can be highly inconvenient. 

4. Walk Us Through How You Would Test Lambda Functions Without Writing Scripts? 

Lambda has simple testing techniques that make such applications easy. Its management console comes with a Graphical User Interface for testing different functions. For this case, I would configure the suitable trigger event, provide the function to be tested with the relevant input, save the test and wait for AWS Lambda to invoke the function. This means clicking on Actions, selecting the Configure test event option in the drop-down list, and then keying in the input in JSON format. Once the Lambda function is invoked and the input passed, the result will be available in the execution result area. 

5. Can You Create Different Versions Of Functions In AWS? 

Yes. Lambda is quite flexible and allows users to create different versions of their lambda functions.  Once created, the new version is separated from the original one to facilitate individual testing, after which it can be published and made official. This is possible thanks to Lambda API. When given such a command, it returns a JSON report with a function version number and a unique resource number for referencing the unpublished version of the function. 

6. How Would You Make Different Lambda Functions Work Together In A Complex Workflow? 

I would build modular lambda functions focusing on specific tasks and then create a step function for invoking each function depending on the given conditions. These test functions are usually responsible for different aspects of such an arrangement. They allow various components to coordinate with one another, even giving them another chance if they fail the first time. They also use state machines to monitor the states of different tasks. State machines are created in the Graphical User Interface. 

7. What Do You Understand By AMI 

AMI refers to Amazon Machine Image. It is more of a template with an operating system, several programs, and an application server. Its copy can be easily generated in the cloud, where it can operate a virtual server. The Amazon Machine Image comes with several instances which can run simultaneously, making it a vital utility in AWS Lambda. 

8. How Does AWS Lambda Contribute To Faster Development 

AWS Lambda has a serverless architecture with several advantages, such as faster development.  This architecture supports rapid innovation, which translates into fewer operational issues. It also allows flexible technology stack updates, saving product engineers time. Users or product engineers can, therefore, entirely focus on the actual business logic of the application since all the system engineering problems have been taken care of. This is why AWS Lambda is quite popular in the business community. 

9. What Are Some Of The Events Sources That Can Trigger A Lambda Function? 

Event sources publish events which are then processed by Lambda functions. Familiar event sources include data stores that trigger an event to call the lambda function when we track data change; endpoints such as Alexa command and HTTP/Websocket from API Gateway; repositories and message services. Repositories such as Github can trigger a lambda function when CodeCommit is used to execute CI/CD action build. A lambda function is activated on message services when a new message is added to SQS or via an SNS Notification. All these events determine how AWS lambda runs codes, given that it is a serverless service. 

10. What Are The Types Of Storage Available In AWS Lambda? 

AWS Lambda supports all the storage options provided by Amazon, which can also be used together, given that they are all durable and high-performing. The first tool, EBS, offers block-level storage. It has encryption features making it the best option for systems that require independent storage. The second option, Amazon S3, is a cheap alternative with no data storage limits. The third option is EC2 instances, connected to the host PC as storage disks. It is a temporary storage option that can act as an alternative as the user thinks of a better storage option. The last option is adding storage, a root storage device that can be used to launch instances. 

11. Define Automated Deployment And Auto Scaling In AWS Lambda. 

Automated deployment refers to the rapid deployment of a given software to testing and production environments. It comes in handy in AWS thanks to its ability to rise above various human interferences. It also ensures the best quality-based outcomes in different parameters. On the other hand, auto-scaling is an AWS Lambda feature that allows for the automatic configuration and spinning of novel instances. It enables users to monitor all occurrences through thresholds and metrics, provided they cross a threshold and introduce no interference. 

12. Do You Know How To Automate A Serverless Application? 

Having Used AWS Lambda for quite some time, I am confident in my ability to automate serverless applications. For AWS Lambda, I would use the AWS pipeline, which offers a continuous delivery and serverless application release by modeling, visualizing and automating all the needed steps. Another option is AWS CodeDeploy which has an automated deployment engine for Lambda-based applications. The CodeDeploy coordinates deployments based on the established best-practice methodologies, such as linear and canary deployments. It also ensures that a newly deployed program is secure, stable and ready for use by permitting the development of significant barriers. 

13. Mention Some Of The Best Practices When Automating Deployments With AWS Cloud Formation 

I always observe eight best practices when automating deployments with AWS Cloud formation. One, I check whether whatever I plan to deploy has already been developed or shared with the community and use whatever I find as my first template to save hours of effort. Two, I usually create modular or several smaller templates that can be easily reused in the future. The third best practice is using existing repositories as submodules, saving time and lessening the need to maintain redundant resources. The other five best practices are: using an integrated development environment with lint, using parameters to define paths to external assets, using similar names for standard parameters, automating AWS Cloud formation testing with TaskCat and lastly, maintaining all the templates. 

14. How Would You Ensure Security In Lambda? 

Lambda has a feature known as IAM, or Identity Access and Management, which makes it a relatively secure platform. An administrator can also grant or revoke user access to specific roles, an option I would use to ensure that unauthorized users do not access what they should not. Lastly, I would update all the available security protocols to avoid surprises. 

15. Mention How Lambda Works And All The Things It Can Build

AWS Lambda is an easy-to-use platform that doesn’t require much input.  Once a code is uploaded to AWS Lambda and set up to trigger from other AWS services, mobile applications and HTTP endpoints, Lambda runs it the moment it triggers using only the required computing resources. Some of the things one can achieve with AWS Lambda include data validation, real-time file processing, data processing, third-party API requests, filtering and real-time stream processing sorting. 

16. How Does AWS Lambda Work And How Is Its Cost Determined? 

AWS Lambda’s working mechanism is outstanding, given that it runs code based on specific events, such as data change in an S3 bucket or an HTTP request. The platform automatically provides the resources needed to run the code when an event occurs, which are only released when the code execution ends. On cost, AWS Lambda is billed based on the number and duration of requests and the amount of memory configured for functions. When billing, the code execution duration is rounded to 100ms. 

17. Define A Trigger And Walk Us Through How You Would Configure One For An AWS Lambda Function 

A trigger in AWS Lambda is what executes a function. Triggers are typically configured to respond to events such as data changes in an S3 bucket. They ensure that the platform/ service automatically executes a function in the occurrence of such events. To configure a trigger, I would go to the management console, click on the target function, and then select the “+ Add trigger” button in the ‘Designer’ section. Lastly, I would choose the type of trigger I am targeting, such as a Kinesis stream. 

18. How Are Lambda Functions Tested And Scaled? 

AWS Lambda functions are tested using the “Test” button in the management console, which allows simulation function-triggering events and reveals an output. An alternative is using CLI to invoke a function with test event data. Scaling in Lambda AWS happens automatically depending on the number of requests received. Lambda releases more resources to handle more load when requests increase. The platform also has an auto-scaling service that allows users to set up scaling policies for the automatic scaling of functions guided by specific metrics. 

19. How Can One Debug And Secure A Lambda Function? 

The AWS Management Console and AWS CSI allow AWS users to view logs and identify issues for debugging purposes. Alternatively, one can use the included X-Ray service that debugs and traces functions’ execution or the AWS Step Functions that generates a visual workflow of processes allowing users to identify the source of a given issue. 

On securing a lambda function, one can use IAM roles to regulate access to a specific function and the related resources. Other options include using the Key Management Service to encrypt confidential data stored in the function and the environment variables and using security groups to regulate network access to a given function. These features make Lambda a relatively secure platform. 

20. How Do You Think Lambda Compares To Other Serverless Computing Options? 

Other popular serverless computing options include Google Cloud Functions and Azure Functions. Even though they play the same role as AWS Lambda, features such as pricing, language and framework support, and scalability may differ. For example, AWS Lambda supports more languages and frameworks than Azure Functions and Google Cloud Functions, which support four and three, respectively. Additionally, AWS Lambda allows adding several event sources to one function, allowing the uncoupling of the development sources from the integration sources while the other two do not. 

21. How Do You Normally Minimize The Cold Start Effect When Using AWS Lambda? 

I have four ways of minimizing the cold start effect that has significantly improved my AWS Lambda experience. I normally keep my functions small and focused to reduce the number of dependencies or packages and share common dependencies across different functions using the AWS Lambda Layers feature. The two remaining ways are: keeping a few function instances warmed up for quick response to requests thanks to the Provisioned Concurrency feature and using my personal container images with Lambda functions thanks to the AWS Lambda Container Image Support. 

22. How Would You Advise A Junior Developer To Handle AWS Lambda Function Errors? 

I would recommend three solutions that can help them detect present and future errors in their Lambda functions: using CloudWatch alarms, CloudWatch Logs and try-catch blocks. CloudWatch Logs allow easy monitoring of functions and detection of any errors incurred during execution, while CloudWatch Alarms send notifications in the event of an error. Lastly, try-catch block inclusion in codes allows the detection of specific exceptions and the return of the right error message to the client. 

23. What Is The Role Of Kinesis In AWS Lambda? 

Kinesis is an AWS service that allows users to collect, process, and analyze real-data streams. Developers can set up and configure a Kinesis stream to trigger Lambda functions, allowing the functions to automatically process a new data record when added to the stream. Additionally, Kinesis offers a Data Firehouse service that allows users to set up a data records stream and configure the Lambda function as a transform, allowing processing and transformation of records before sending them to their destination. 

24. How Would You Version, Deploy, And Connect A Lambda Function To A VPC? 

I would create and publish a new version of the function using the AWS Management Console or AWS CLI and then use then automate the deployment process through the AWS CodeDeploy service. Once deployed, I would use the AWS CodePipeline service to build a continuous delivery pipeline for the function.

To connect the function to a PVC, I would first create a VPC and its subnets in my account before creating a security group to allow easy traffic flow in and out of the function. I would then specify the VPC, subnets and, lastly, the security groups to use by updating the function’s configuration- a process that would take little time. 

25. Can Lambda Be Used With Other AWS Services? 

Yes. Lambda is compatible with various AWS services such as SQS, DynamoDB, Kinesis, and S3, which it engages in creating serverless applications. Lambda is commonly used to process the data stored in an S3 bucket and to automatically generate SNS messages when DynamoDB receives new items in its tables, showing how these services complement each other. Lambda also uses Kinesis to process real-data streams thanks to Kinesis Data Firehose and Data Streams features. 


These 25 recommendations sum up some of the most common questions in AWS Lambda interviews used to determine a candidate’s skill level. Therefore, you must ensure that you are well-versed in the technical aspects of AWS Lambda to succeed in your upcoming interview. We wish you all the best, and also remember to give the interviewer an excellent first impression.