Serverless Compute (Lambda)

Question 1

What is a Microservices Architecture?

Answer 1

o A Microservices Architecture is the opposite of a Monolithic Architecture: instead of having all system functions in one codebase, components are separated into microservices and operate independently. Operations, updates and scaling can be done on a per-microservice basis
o Microservices allow direct communication between components and end user. If one part of the system requires more capacity, that service alone can be scaled and updated as needed

Question 2

What are APIs?

Answer 2

o An API (Application Programming Interface) is an interface accessed ( = consumed) by another service or application
o An API Endpoint hosts one or more APIs and makes them available on a network (private or public internet). APIs remain static – they are abstracted from what the code inside the service is doing. API consumers don’t care how things are done, only that the interface works

Question 3

What is an Event-Driven Architecture?

Answer 3

o When using an Event-Driven Architecture, a system operates around events that represent an action or a change of state (a button being clicked, a file being uploaded, the temperature dropping below a certain level). It is efficient because events are generated and pushed, rather things being continuously polled (polling requires always-on compute and does not scale well)

Question 4

What is a Serverless Architecture?

Answer 4

o Serverless Architectures consists of 2 main principles:
 Backend as a Service (Baas): using 3rd-party services where possible, rather than running your own (e.g. Auth0 or Cognito for Authentication, Firebase or DynamoDB for Data Storage)
 Function as a Service (Faas): using event-driven architecture where possible. The functions defining the applications are only active (= invoked) when needed, i.e. when an event is received

Question 5

What is Lambda?

Answer 5

o Lambda is a FaaS product. Functions are code, which is executed in a runtime. Functions are invoked by events, perform actions for up to 15 minutes, and then terminate. Functions are stateless – each run is clean
o Functions can consume internet API endpoints or other services
o Functions can be allowed access to VPCs – allowing private resource access
o Lambda support many prebuilt runtimes, and custom ones can be created
o Access to AWS services is provided by the function’s execution role. This role is assumed by Lambda, and temporary security credentials are available to the function via STS

Question 6

What is API Gateway?

Answer 6

o API Gateway is a managed API endpoint service. It can be used to create, publish, monitor and secure APIs as a service. API Gateway can use other AWS services for compute (FaaS/IaaS) as well as to store and recall data
o APIs can be migrated to API Gateway in a monolithic form, and gradually moved to a microservices architecture, and then, once components have been fully broken up, a serverless and FaaS based architecture
Monolith ==> Microservice ==> Serverless

Question 7

What is Step Functions?

Answer 7

o Step Functions is a serverless visual workflow service that provides state machines
o It replaces SWF (Simple Workflow Service) for server based workflows
o A State Machine can orchestrate other AWS services with simple logic, branching and parallel execution, and it maintains a state; they can perform work via tasks
o Step Functions allows for long-running serverless workflows (up to 1 year), overrunning the limitation of Lambda being stateless and limited in execution to 15’
o A State Machine can be defined using Amazon State Language (ASL)