AWS Lambda Interview Questions & Answers (2025)

AWS Lambda is one of the best computing services in the market, which is serverless. It allows you to run codes without the help of managing servers or provisioning. You have to pay for the computing time when you consume data. There are no charges to be paid when you are not running your code. Using Lambda, you can quickly run codes for any application or backend service virtually, without any administration. You have to upload the code and rest everything is taken care of by Lambda. Lambda runs and scales your code with high availability. You can even set the code up to trigger from the other AWS available or give it a call directly from the mobile app or any web.

Lambda imposes very few restrictions on operating system activities and standard language. However, there are few of the activities that have been disabled like for instance, inbound network connections and trace calls, which is a debugging system, and TCP port 25 traffic as a measure to anti-spam. For outbound connections IP/TCP sockets are supportive.

The complete execution has to take place within 300 seconds from placing the calls to AWS Lambda. 3 seconds is the default timeout however you can set any timeout value between 1 to 300 seconds

What Lambda does is, it stores the code in the Amazon S3 and encrypts it when it is resting. AWS Lambda is known to perform an additional integrity check while the code is running.

AWS Lambda offers you an easy way to get many activities done in the cloud. Like for instance, AWS Lambda can be used to build mobile back-ends from Amazon DynamoDB to retrieve and transform data. Handlers that transform and compress objects as they get uploaded to Amazon S3, using Amazon Kinesis the server-less processing of streaming data, and reporting and auditing of the API calls that are made to any Web Services of Amazon are other activities can be done in the cloud with the help of AWS Lambda.

It is a feature available in the Web services of Amazon that helps you enable to spin and configure the novel instances automatically. At any stage, you don’t have to interfere, and one can quickly do the monitoring using thresholds and metrics. You merely have to cross the threshold to enable the task and instances without any interference that may have increased horizontally.

AWS Lambda supports the codes that are written in Python, C# (.NET Core), Node.js (JavaScript), Java (Java 8 compatible), and Go. The code can also include existing libraries and even the native ones.

No. As AWS Lambda starts operating the compute infrastructure on behalf of the user,  the foundation on which AWS Lambda runs is not accessible. It allows Lambda to apply security patches, perform health checks, and work out other routine maintenance.

Absolutely yes! You can efficiently use custom as well as NPM packages to be precise.

AWS Lambda has been so designed to use redundancy and replication so that it provides high availability for both, lambda functions it operates on and the service it provides. Maintenance windows and scheduled downtimes for Lambda functions.

The default limit is applicable only at the account level. So no, there is no default limit applied at a functional level.

The server-less application’s release process can be automated by using an AWS CodePipeline and also an AWS CodeDeploy.  The CodePipeline is a continuous form of delivery service that is enabled with modeling, visualizing and automating the steps that are required, so that server less application can be released. CodeDeploy also comes with a deployment engine that is automated for Lambda-based applications. It lets you coordinate deployments as per the best-practice methodologies established like a canary and linear deployment, and assists you to develop significant barriers to ensure that the newly-deployed program is secure, stable, and ready for industrial use.

For getting started, the console of AWS Lambda has to be visited, and a blueprint has to be downloaded. The file downloaded will have an AWS SAM file (which is used to define AWS resources in the application), and a.ZIP file (which includes the function’s code). The AWS CloudFormation commands can then be used for packaging and deploying the serverless application just downloaded. For further details, visit the documentation.

Lambda function can be enabled for tracking, with AWS X-Ray by addition of X-Ray permissions to Lambda function’s role of execution and changing the function’s “mode of tracing” to “active.” When you enable X-ray for Lambda function, AWS Lambda shall emit the tracing information to X-Ray with information about the Lambda service that incurred while invoking the function. This shall provide you with information such as the overhead of Lambda service, the function unit time, and time for function execution. Also, the X-Ray SDK can be included in Lambda deploying the package to create one’s segments of the trace, annotate one’s marks, or view the trace segments for various downstream calls that are made from Lambda function. X-Ray SDKs are presently available for Node.js and Java. Visit the Troubleshooting applications based on Lambda to learn more. AWS X-Ray rates shall apply.

Yes. When a Lambda function is updated, there shall be a brief period, less than a minute, when requests can be served by either the old or the new version of the function.

No. The AWS Lambda is designed so that it can run some instances of functions simultaneously. However, AWS Lambda has a by default safety threshold for some consecutive runs for every account per region. The maximum successive executions for single AWS Lambda functions can be controlled which can be used to reserve a portion of the account concurrency threshold for the critical functions or lower traffic rates to downstream the resources.

If you so wish to submit a query to increase the limit, you can refer to the Support Centre for more.

Upon exceeding the threshold limit, the AWS Lambda functions are being called synchronously and will return a threshold error (429 error- code). The tasks of Lambda functions that are called asynchronously shall absorb the reasonable traffic bursts for 15-30 minutes, after which the incoming events shall be rejected as they are throttled. In case the Lambda function is being called in response to the Amazon S3 events, events that are rejected by AWS Lambda may be retained back and retried by S3 for 24 hours. The events coming from streams of Amazon Kinesis and Amazon DynamoDB are retried along as the Lambda function doesn’t succeed, or the data doesn’t expire. Amazon Kinesis and Amazon DynamoDB Streams hold the data for 24 hours.

The applications which are Lambda-based (are also referred to as the server-less applications) are made of functions that are triggered by various events. A default server-less application consists of one or more of such functions that are triggered by the events such as object upload to Amazon S3, Amazon SNS, or API actions. The functions can work alone or make use of other resources like DynamoDB tables or buckets of Amazon S3. The most default serverless application is a function.

Firstly, this approach has simple operations which provide quick time to market and better sales. Users need to only pay for when the code is compiling, and many costs can be saved by enhancing the profits. Also, managing the components of the broader application is not a big deal. In addition to this, it is not needed to have the additional infrastructure. The most significant benefit is that consumers do not need to worry about the servers on which the code is executed.

Everything comes with its own merits and demerits depending on the task performed. Coming to the server-less approach, this fact is applicable here as well. In a few cases, their upper limit is strictly on the vendor control in this approach, and this means more downtime and thus more losses. The loss of system functionality and the system’s limits are other issues. Also to mention, no dedicated hardware is available for the server-less approach. Thus performance and security have become essential challenges at various stages. Sometimes errors by the customer can also give rise to the problems. New deployments, as well as the monitoring tools, have become the sole choice when the matter is of converting to functions of Google Cloud.