Serverless vs container decision in AWS - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Choosing between serverless and containers for a bursty workload

You have a web application with unpredictable traffic spikes that last only a few minutes. Which deployment option is best to handle this efficiently?

A Use serverless functions that automatically scale with demand and charge per execution.

B Use containers on EC2 instances with fixed capacity to handle peak load.

C Use containers on a single large EC2 instance to simplify management.

D Use serverless functions but limit concurrency to avoid scaling.

💡 Hint

Think about cost and automatic scaling for short bursts.

Serverless functions scale automatically and you pay only for actual usage, making them ideal for unpredictable, short bursts. Containers on fixed EC2 instances may waste resources or fail to scale quickly.

❓ Architecture

intermediate

Designing a microservices app with mixed compute needs

You are designing a microservices app where some services need long-running processes and others are event-driven and short-lived. Which architecture fits best?

A Use containers for long-running services and serverless for short-lived event-driven ones.

B Deploy all services as containers to unify deployment.

C Deploy all services as serverless functions for simplicity.

D Use serverless for long-running services and containers for short-lived ones.

💡 Hint

Consider which compute model suits long-running versus short-lived tasks.

Containers are better for long-running processes because serverless functions have execution time limits. Serverless is ideal for short-lived, event-driven tasks due to automatic scaling and cost efficiency.

❓ security

advanced

Security considerations for serverless vs containers

Which security concern is more critical when using containers compared to serverless functions?

A Handling automatic scaling to prevent denial of service.

B Ensuring function execution time limits are not exceeded.

C Managing the underlying OS patching and vulnerabilities.

D Configuring event triggers securely.

💡 Hint

Think about who manages the OS in each model.

Containers require you to manage the OS and patch vulnerabilities, while serverless abstracts this away. Execution time limits and event triggers are more relevant to serverless.

❓ service_behavior

advanced

Cold start impact on serverless functions

What is the main impact of cold starts in serverless functions on user experience?

A Failure to execute the function on first request.

B Longer initial response time when a function is invoked after inactivity.

C Permanent downtime until function is redeployed.

D Increased cost due to longer execution time.

💡 Hint

Consider what happens when a function is called after not being used for a while.

Cold starts cause a delay in the first invocation after inactivity, leading to longer response times. They do not cause failures or permanent downtime.

✅ Best Practice

expert

Optimizing cost and performance in hybrid serverless-container apps

You run a hybrid app with containers for core services and serverless for auxiliary tasks. Which practice best optimizes cost and performance?

A Keep containers running at full capacity 24/7 and use serverless only for peak loads.

B Use serverless for all tasks to avoid managing containers.

C Convert all container services to serverless to unify billing.

D Scale containers dynamically based on load and use serverless for unpredictable, short tasks.

💡 Hint

Think about scaling and cost efficiency for different workload types.

Dynamic scaling of containers saves cost and matches performance needs. Serverless suits unpredictable short tasks. Running containers at full capacity wastes resources. Converting all to serverless may not fit long-running needs.

Practice

1. Which AWS service lets you run code without managing servers, automatically scaling with demand?

easy

A. Amazon ECS

B. AWS Lambda

C. Amazon EC2

D. AWS Elastic Beanstalk

Solution

1. Step 1: Understand serverless concept

   Serverless means you don't manage servers; code runs on demand.

2. Step 2: Identify AWS service matching serverless

   AWS Lambda runs code without server management and scales automatically.

3. Final Answer:

   AWS Lambda -> Option B

4. Quick Check:

   Serverless = AWS Lambda [OK]

Hint: Serverless means no servers to manage, pick Lambda [OK]

Common Mistakes:

• Choosing EC2 which requires server management
• Confusing containers with serverless
• Picking Elastic Beanstalk which manages servers but not fully serverless

2. Which AWS service is best described by this syntax snippet for deploying a container?

aws ecs create-cluster --cluster-name myCluster

easy

A. Amazon S3 bucket creation

B. AWS Lambda function deployment

C. Amazon ECS container cluster creation

D. AWS CloudFormation stack deployment

Solution

1. Step 1: Analyze the command

   The command uses 'aws ecs create-cluster' which is for ECS clusters.

2. Step 2: Match command to service

   ECS is AWS service for managing containers in clusters.

3. Final Answer:

   Amazon ECS container cluster creation -> Option C

4. Quick Check:

   "aws ecs create-cluster" = ECS container cluster [OK]

Hint: ECS commands manage containers, Lambda uses different syntax [OK]

Common Mistakes:

• Thinking this command deploys Lambda functions
• Confusing S3 bucket commands with ECS
• Assuming CloudFormation syntax

3. You have a web app that needs to run continuously with custom OS settings. Which AWS option fits best?
Options:
A) AWS Lambda
B) AWS CloudFront
C) Amazon S3
D) Amazon ECS with Fargate

medium

A. AWS Lambda

B. AWS CloudFront

C. Amazon S3

D. Amazon ECS with Fargate

Solution

1. Step 1: Identify app requirements

   The app runs continuously and needs custom OS settings, so it needs control over environment.

2. Step 2: Match service to requirements

   AWS Lambda is event-driven and short-lived, not continuous. ECS with Fargate runs containers continuously with environment control.

3. Final Answer:

   Amazon ECS with Fargate -> Option D

4. Quick Check:

   Continuous app + custom OS = ECS Fargate [OK]

Hint: Continuous with custom OS? Choose containers (ECS) not Lambda [OK]

Common Mistakes:

• Choosing Lambda for continuous workloads
• Confusing S3 (storage) or CloudFront (CDN) as compute
• Ignoring environment control needs

4. You tried running a container on AWS Lambda but it failed. What is the likely cause?

medium

A. Lambda does not support running containers longer than 15 minutes

B. Lambda requires a Dockerfile to deploy containers

C. Lambda only supports Python code, not containers

D. Lambda cannot run containers at all

Solution

1. Step 1: Understand Lambda container support

   Lambda supports container images but has a max execution time of 15 minutes.

2. Step 2: Identify cause of failure

   If container runs longer than 15 minutes, Lambda will fail the execution.

3. Final Answer:

   Lambda does not support running containers longer than 15 minutes -> Option A

4. Quick Check:

   Lambda container max time = 15 minutes [OK]

Hint: Lambda containers have 15-minute max runtime limit [OK]

Common Mistakes:

• Thinking Lambda cannot run containers at all
• Believing Lambda only supports Python code
• Confusing Dockerfile requirement

5. Your startup wants to minimize costs and avoid managing servers for a new app with unpredictable traffic spikes. Which AWS approach is best?

hard

A. Deploy on AWS Lambda for automatic scaling and no server management

B. Use Amazon ECS with EC2 instances for full control

C. Host on Amazon EC2 with manual scaling

D. Use AWS Elastic Beanstalk with fixed server capacity

Solution

1. Step 1: Analyze startup needs

   Startup wants to minimize costs and avoid managing servers, with unpredictable traffic.

2. Step 2: Match AWS service to needs

   AWS Lambda automatically scales with traffic and requires no server management, reducing cost and effort.

3. Step 3: Compare other options

   ECS with EC2 or Elastic Beanstalk requires server management or fixed capacity, increasing cost and complexity.

4. Final Answer:

   Deploy on AWS Lambda for automatic scaling and no server management -> Option A

5. Quick Check:

   Min cost + no servers + spikes = Lambda [OK]

Hint: No servers + spikes? Pick Lambda for auto scaling [OK]

Common Mistakes:

• Choosing ECS or EC2 which need server management
• Assuming Elastic Beanstalk auto-scales without servers
• Ignoring cost and management factors