Fargate vs EC2 launch type in AWS - Performance Comparison

Time Complexity: Fargate vs EC2 launch type

O(n)

Understanding Time Complexity

We want to understand how the time it takes to run tasks changes when using Fargate or EC2 launch types in AWS ECS.

Specifically, how does the number of tasks affect the time and operations involved?

Scenario Under Consideration

Analyze the time complexity of launching multiple ECS tasks using Fargate and EC2 launch types.

// Using Fargate launch type
for (let i = 0; i < n; i++) {
  ecs.runTask({
    launchType: 'FARGATE',
    taskDefinition: 'myTaskDef',
    networkConfiguration: {...}
  });
}

// Using EC2 launch type
for (let i = 0; i < n; i++) {
  ecs.runTask({
    launchType: 'EC2',
    taskDefinition: 'myTaskDef',
    cluster: 'myCluster'
  });
}

This sequence runs n tasks either on Fargate or EC2, one task per API call.

Identify Repeating Operations

Look at what repeats as we increase tasks.

• Primary operation: The ecs.runTask API call to start each task.
• How many times: Exactly n times, once per task.
• Additional difference: EC2 requires managing container instances, which involves extra background operations but not per task API calls.

How Execution Grows With Input

As the number of tasks n grows, the number of API calls grows the same way.

Input Size (n)	Approx. Api Calls/Operations
10	10 runTask calls
100	100 runTask calls
1000	1000 runTask calls

Pattern observation: The number of API calls grows linearly with the number of tasks.

Final Time Complexity

Time Complexity: O(n)

This means the time and number of operations increase directly in proportion to the number of tasks you run.

Common Mistake

[X] Wrong: "Launching tasks on Fargate is faster because it uses fewer API calls than EC2."

[OK] Correct: Both launch types require one API call per task; the difference is in how resources are managed behind the scenes, not in the number of calls.

Interview Connect

Understanding how task launch scales helps you design systems that handle growth smoothly and explain your choices clearly in discussions.

Self-Check

What if we batch multiple tasks in a single API call? How would the time complexity change?

Practice

1. What is the main difference between AWS Fargate and EC2 launch types for running containers?

easy

A. Fargate runs containers without managing servers, EC2 requires managing servers.

B. Fargate requires managing servers, EC2 runs containers without servers.

C. Both require managing servers but use different operating systems.

D. Both run containers without any server management.

Solution

1. Step 1: Understand Fargate's server management

   Fargate abstracts server management, so you don't handle servers directly.

2. Step 2: Understand EC2 launch type server management

   EC2 launch type requires you to manage the servers where containers run.

3. Final Answer:

   Fargate runs containers without managing servers, EC2 requires managing servers. -> Option A

4. Quick Check:

   Server management difference = D [OK]

Hint: Fargate = no servers to manage, EC2 = you manage servers [OK]

Common Mistakes:

• Confusing which launch type manages servers
• Thinking both require server management
• Assuming Fargate needs server setup

2. Which of the following is the correct way to specify the launch type as Fargate in an ECS service JSON?

easy

A. "launchType": "EC2"

B. "launchType": "FARGATE"

C. "launchType": "Serverless"

D. "launchType": "Container"

Solution

1. Step 1: Check valid launch type values in ECS

   ECS supports "EC2" and "FARGATE" as launch type values in uppercase.

2. Step 2: Identify correct Fargate syntax

   The correct string for Fargate is "FARGATE" in uppercase letters.

3. Final Answer:

   "launchType": "FARGATE" -> Option B

4. Quick Check:

   Fargate launch type syntax = A [OK]

Hint: Use uppercase "FARGATE" for launchType in ECS JSON [OK]

Common Mistakes:

• Using lowercase "fargate" instead of uppercase
• Using invalid launch type names like "Serverless"
• Confusing EC2 and Fargate strings

3. Given this ECS service configuration snippet, what launch type will it use?

{
  "launchType": "EC2",
  "taskDefinition": "my-task-def"
}

medium

A. It will run containers on EC2 instances you manage.

B. It will run containers on AWS Fargate without server management.

C. It will fail because "EC2" is not a valid launch type.

D. It will run containers on Lambda functions.

Solution

1. Step 1: Read the launchType value

   The launchType is set to "EC2" which means containers run on EC2 instances.

2. Step 2: Understand EC2 launch type behavior

   EC2 launch type requires you to manage the servers where containers run.

3. Final Answer:

   It will run containers on EC2 instances you manage. -> Option A

4. Quick Check:

   launchType "EC2" means managed servers = A [OK]

Hint: launchType "EC2" means you manage servers [OK]

Common Mistakes:

• Thinking "EC2" means serverless
• Assuming "EC2" is invalid syntax
• Confusing EC2 with Lambda

4. You tried to deploy an ECS task with this launch type: "launchType": "fargate" but got an error. What is the likely cause?

medium

A. Fargate launch type is not supported in ECS.

B. The launch type should be a boolean, not a string.

C. You must specify the launch type as "EC2" for tasks.

D. The launch type value is case-sensitive and must be uppercase "FARGATE".

Solution

1. Step 1: Check launch type case sensitivity

   ECS launch type values are case-sensitive and require uppercase strings like "FARGATE".

2. Step 2: Identify error cause

   Using lowercase "fargate" causes a validation error because it's invalid syntax.

3. Final Answer:

   The launch type value is case-sensitive and must be uppercase "FARGATE". -> Option D

4. Quick Check:

   Case-sensitive launchType = B [OK]

Hint: Use uppercase "FARGATE" to avoid launch type errors [OK]

Common Mistakes:

• Using lowercase launch type values
• Thinking Fargate is unsupported
• Confusing data types for launchType

5. You want to run a containerized app with minimal server management and automatic scaling. Which launch type should you choose and why?

hard

A. EC2 launch type, because it gives full control over servers and scaling.

B. EC2 launch type, because it is cheaper and requires no scaling setup.

C. Fargate launch type, because it removes server management and handles scaling automatically.

D. Fargate launch type, because it requires manual server setup but better performance.

Solution

1. Step 1: Identify launch type for minimal server management

   Fargate removes the need to manage servers, unlike EC2 which requires server control.

2. Step 2: Consider automatic scaling capabilities

   Fargate automatically scales containers based on demand without manual server scaling.

3. Final Answer:

   Fargate launch type, because it removes server management and handles scaling automatically. -> Option C

4. Quick Check:

   Minimal management + auto scaling = Fargate = C [OK]

Hint: Choose Fargate for no servers and auto scaling [OK]

Common Mistakes:

• Choosing EC2 for minimal management
• Assuming EC2 auto scales automatically
• Thinking Fargate needs manual server setup