We have built a news website with more than a billion views per month and we are sharing the learnings from that experience covering Serverless architectures, Design considerations, and Gotchas.

1. Cloud Security Automation| |
Advanced ServerlessApplicationArchitectureand Design
Considerations
DILIPKUMARKOLA,Co-founderandCTO, Tensult | 24th April2019

2. What is Serverless?
• Serverless is, running the workloads on the Cloud without thinking
about servers.
• Examples:
• Hosting an angular frontend website on AWS S3 bucket.
• Implementing a backend API using AWS API Gateway, AWS Lambda and AWS
DynamoDB.
• Processing files when they get uploaded to AWS S3 bucket.
• Send notifications to users using AWS SES when you sign up on the website.
• And these are just a very few examples.

3. Why Serverless?
Scalability AutomationFaster DeploymentsReduces Cost Low Maintenance

4. Large Scale multi-lingual news
website
100% Serverless on AWS
<12 months from concept to
production
CaseStudy News Website

5. 1
DevOps
Engg
>1 Bn Page
Views per
month
60 Mn
Monthly
Active
Users
7
languages

6. CMS Architecture
Authorization of backend users
Cognito
User Pool
CMS
Application
API
Gateway
CMS
API
CloudFront
Cognito
Identity Pool
S3
DynamoDB Lambda Elastic
Search
Populating to ES to enable search
Lambda S3
Sitemaps and RSS feeders
CMS User
For storing photos and videos

7. News Website Architecture
API
Gateway
Website
API
CloudFront
DynamoDB
Elastic
Search
S3
Web User
Sitemaps and RSS feeders
News Data Retrieval

8. NewsletterArchitecture
CloudWatch
Rule
Fetch Newsletter
Template
S3
Cache
Elastic
Search
Fetch List of
Users
Send Newsletter
SES
SNS
Send Token to
fetch next
User List
Newsletters Function
Lambda

9. How Does AWSLambdaWork?
• Function as a Service from AWS.
• Upload function code written in
• NodeJS, Java, Python, Go, Ruby, .Net etc.
• Lambda creates a docker image and executes them
• Automatically scales based on the requests.
• Supports Pull and Push models.
• In Pull model, the Lambda trigger reads the events from streams and processes them.
• In Push model, we need to call Lambda function directly using API (API Gateway)
• Billing is based on the memory allocated and duration of execution.

10. Key Aspects in Design

11. Lambda DesignConsiderations
• Avoid loops in Data flows
• Remember about Cold Starts
• Avoid duplication of code
• Add caching where possible
• Tune the function configuration
• Use versions and aliases
• Treat global variables as constants
• Know what you are logging

12. AWS Lambda scales very fast so if there is any loop in the data flow then it will keep on creating
new containers to handle the new requests leading the bill to shoot up very fast so before
deploying any serverless solution first fully understand the data flow and make sure there are
no loops.
• To detect loops keep monitoring
• Invocation count
• Billing
Avoidloops inthe Data flows
S3 Lambda
Store thumbnails images
Generate thumbnails

13. • AWS Lambda takes some time to start the first container and also the container will be
removed when it idle some time.
• Solution:
• We can keep calling the AWS Lambda function every one minute using AWS CloudWatch event
rules.
• Refactor the function code to start faster by lazily loading the components.
RememberaboutCold Starts
CloudWatch
Rule
Lambda
Pinger

14. Avoidduplication of code
• It is a common danger in FaaS or microservice implementations as there are many
decoupled components so developers tend to duplicate the same code at multiple places
and this can become really unmanageable.
• Define common code as libraries and reuse them in various functions and microservices.
• Incase of NodeJS environment, we can refer common libraries as dependencies using local
directory paths.
• AWS Lambda service provides a feature called Layers in order to share the common code
and libraries across multiple Lambda functions.

15. Addcaching where possible
• AWS Lambda scales but there are limits and our limit is 2500 concurrent executions and
we were hitting this limit and afterwards we added caching on top of the APIs.
• When we send a push notification to our mobile users, we get more than 50K requests
per second to our backend Lambda functions and AWS Lambda used to throttle us.
• Then we restricted access to our API end points via CDN for mobile users as the requests
are getting cached at CDN and only cache misses reaches to backend so considerably
load is reduced on the backend Lambda functions.
• So keep monitoring for throttles and errors.

16. Tune the function configuration
• Memory determines both CPU and RAM allocated to function
• Low memory doesn’t always means cost effective as it leads to low CPU, so
requests might take more time leading to you paying even more.
• Try different memory settings and analyze the request execution times
then choose appropriate memory setting.
• Don’t forget to tune this setting after every major update to the function.

17. Use versions andaliases
• When updating the function make sure to create a new version.
• This allows us to easily roll back the functions incase of failures.
• We can also use aliases for A/B testing by pointing our APIs to a different alias.
• Be aware of limits on storage and then decide the number of versions needed.
Source

18. Treatglobal variablesas constants
• AWS Lambda cache all the global variables and context across the
requests so we can't change the global variables while requests are
processing. If we do that then the data might get corrupted.
• Solution:
• Code review before deploying the functions to Lambda.
• Do thorough testing in dev/staging environments before pushing functions to
prod environment.

19. Know what you arelogging
• Lambda integrates with CloudWatch for logs and CloudWatch provides
good searching features but ingestion cost is high, so in the production only
log warnings and errors.
• Set retention for logs appropriately, by default logs in CloudWatch service
are retained forever but that may not be necessary for business case.
• In case you need to keep logs for a very long time for compliance reasons
then move them to S3/Glacier services.

20. AboutUs
• Founded in 2017, Tensult is a Technology Consulting Company for the cloud
• Started by passionate, ex-AWS people who brings in-depth cloud knowledge and
expertise
• Automation First approach
• 20+ Happy Customers

21. Thank You
Sample our work
Questions?
Drop us a note at sales@tensult.com
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https://blogs.tensult.com
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