- AWS Lambda offers Serverless computing that allows you to build and run applications and services without thinking about servers, which are managed by AWS
- Lambda lets you run code without provisioning or managing servers, where you pay only for the compute time when the code is running.
- Lambda is priced on a pay per use basis and there are no charges when the code is not running
- Lambda allows you to run code for any type of application or backend service with zero administration
- Lambda performs all the operational and administrative activities on your behalf, including capacity provisioning, monitoring fleet health, applying security patches to the underlying compute resources, deploying code, running a web service front end, and monitoring and logging the code.
- Lambda provides easy scaling and high availability to your code without additional effort on your part.
- Lambda does not provide access to the underlying compute infrastructure
- Lambda is designed to process events within milliseconds. Latency will be higher immediately after a Lambda function is created, updated, or if it has not been used recently.
- Lambda is designed to use replication and redundancy to provide high availability for both the service itself and for the Lambda functions it operates. There are no maintenance windows or scheduled downtimes for either.
- Lambda stores code in S3 and encrypts it at rest and performs additional integrity checks while the code is in use.
- All calls made to AWS Lambda must complete execution within 300 seconds. The default timeout is 3 seconds, but you can set the timeout to any value between 1 and 300 seconds.
Lambda Functions & Event Sources
Core components of Lambda are Lambda functions and event sources.
- An event source is the AWS service or custom application that publishes events
- Lambda function is the custom code that processes the events
- Each Lambda function has associated configuration information, such as its name, description, entry point, and resource requirements
- Lambda functions should be stateless, to allow AWS Lambda launch as many copies of the function as needed as per the demand. State can be maintained externally in DynamoDB or S3
- Each Lambda function receives 500MB of non-persistent disk space in its own /tmp directory.
- Lambda functions have the following restrictions
- Inbound network connections are blocked by AWS Lambda
- Outbound connections only TCP/IP sockets are supported
- ptrace (debugging) system calls are blocked
- TCP port 25 traffic is also blocked as an anti-spam measure.
- Lambda automatically monitors Lambda functions, reporting real-time metrics through CloudWatch, including total requests, latency, error rates, and throttled requests
- Lambda automatically integrates with Amazon CloudWatch logs, creating a log group for each Lambda function and providing basic application lifecycle event log entries, including logging the resources consumed for each use of that function
- Each AWS Lambda function has a single, current version of the code and there is no versioning of the same function. However, versioning can be implemented using Aliases.
- Each Lambda function version has a unique ARN and after it is published it is immutable (that is, it can’t be changed).
- Lambda supports creating aliases for each Lambda function versions.
- Conceptually, an AWS Lambda alias is a pointer to a specific Lambda function version, but it is also a resource similar to a Lambda function, and each alias has a unique ARN.
- Each alias maintains an ARN for a function version to which it points
- An alias can only point to a function version, not to another alias
- Unlike versions, which are immutable, aliases are mutable (that is, they can be changed) and can be updated to point to different versions
- For failures, Lambda functions being invoked asynchronously are retried twice. Events from Kinesis and DynamoDB streams are retried until the Lambda function succeeds or the data expires. Kinesis and DynamoDB Streams retain data for a minimum of 24 hours.
Lambda Event Sources
Refer Blog Post – Lambda Event Source
Lambda Best Practices
- Lambda function code should be stateless, and ensure there is no affinity between the code and the underlying compute infrastructure.
- Instantiate AWS clients outside the scope of the handler to take advantage of connection re-use.
- Make sure you have set +rx permissions on your files in the uploaded ZIP to ensure Lambda can execute code on your behalf.
- Lower costs and improve performance by minimizing the use of startup code not directly related to processing the current event.
- Use the built-in CloudWatch monitoring of your Lambda functions to view and optimize request latencies.
- Delete old Lambda functions that you are no longer using.
AWS Certification Exam Practice Questions
- Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
- AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
- AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
- Open to further feedback, discussion and correction.
- Your serverless architecture using AWS API Gateway, AWS Lambda, and AWS DynamoDB experienced a large increase in traffic to a sustained 400 requests per second, and dramatically increased in failure rates. Your requests, during normal operation, last 500 milliseconds on average. Your DynamoDB table did not exceed 50% of provisioned throughput, and Table primary keys are designed correctly. What is the most likely issue?
- Your API Gateway deployment is throttling your requests.
- Your AWS API Gateway Deployment is bottlenecking on request (de)serialization.
- You did not request a limit increase on concurrent Lambda function executions. (Refer link – AWS API Gateway by default throttles at 500 requests per second steady-state, and 1000 requests per second at spike. Lambda, by default, throttles at 100 concurrent requests for safety. At 500 milliseconds (half of a second) per request, you can expect to support 200 requests per second at 100 concurrency. This is less than the 400 requests per second your system now requires. Make a limit increase request via the AWS Support Console.)
- You used Consistent Read requests on DynamoDB and are experiencing semaphore lock.