Lambda pricing model in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the unit for Lambda memory pricing.

AWS

lambda_memory_price_per_[1] = 0.00001667

Drag options to blanks, or click blank then click option'

AGB-hour

BGB-second

CMB-second

DMB-hour

Attempts:

3 left

💡 Hint

Common Mistakes

Using hours instead of seconds

Using MB instead of GB

The Lambda pricing for memory is charged per GB-second, which means per gigabyte of memory used per second of execution.

2fill in blank

medium

Complete the code to calculate the total Lambda cost given memory in GB and duration in seconds.

AWS

total_cost = memory_in_[1] * duration_in_[2] * price_per_gb_second

Drag options to blanks, or click blank then click option'

AGB

BMB

Cminutes

Dseconds

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing MB with GB

Using minutes instead of seconds

Memory must be in GB and duration in seconds to correctly calculate Lambda cost using the GB-second pricing model.

3fill in blank

hard

Fix the error in the Lambda cost calculation by choosing the correct unit for duration.

AWS

cost = memory_gb * duration_in_[1] * price_per_gb_second

Drag options to blanks, or click blank then click option'

Ahours

Bminutes

Cseconds

Dmilliseconds

Attempts:

3 left

💡 Hint

Common Mistakes

Using minutes or hours instead of seconds

Using milliseconds which is too granular

Lambda duration is billed in seconds, so duration must be in seconds for correct cost calculation.

4fill in blank

hard

Fill both blanks to complete the Lambda pricing formula for total cost.

AWS

total_cost = [1] * [2] * price_per_gb_second

Drag options to blanks, or click blank then click option'

Amemory_gb

Bduration_minutes

Cduration_seconds

Dmemory_mb

Attempts:

3 left

💡 Hint

Common Mistakes

Using MB for memory

Using minutes for duration

The total cost is calculated by multiplying memory in GB by duration in seconds and the price per GB-second.

5fill in blank

hard

Fill all three blanks to complete the Lambda pricing calculation including request count.

AWS

total_cost = ([1] * [2] * price_per_gb_second) + ([3] * price_per_request)

Drag options to blanks, or click blank then click option'

Amemory_gb

Bduration_seconds

Crequest_count

Dduration_minutes

Attempts:

3 left

💡 Hint

Common Mistakes

Using minutes instead of seconds for duration

Confusing request count with duration

The total Lambda cost includes the compute cost (memory GB * duration seconds * price per GB-second) plus the request cost (number of requests * price per request).

Practice

1. What two main factors determine the cost of an AWS Lambda function?

easy

A. Number of requests and compute time

B. Storage size and network bandwidth

C. Number of users and API calls

D. Memory size and database queries

Solution

1. Step 1: Understand AWS Lambda pricing basics

   AWS Lambda charges based on how many times your function runs (requests) and how long it runs (compute time).

2. Step 2: Identify the pricing factors

   Memory size affects compute time cost but the main factors are requests and compute time.

3. Final Answer:

   Number of requests and compute time -> Option A

4. Quick Check:

   Requests + compute time = cost [OK]

Hint: Remember: pay for calls and duration only [OK]

Common Mistakes:

• Confusing storage or bandwidth as pricing factors
• Thinking memory size alone determines cost
• Mixing API calls with requests

2. Which of the following is the correct way to express AWS Lambda pricing units?

easy

A. Memory in MB and network packets

B. Requests per hour and CPU cycles

C. Number of requests and GB-seconds

D. Storage in GB and function calls

Solution

1. Step 1: Recall AWS Lambda pricing units

   Lambda pricing is based on number of requests and compute time measured in GB-seconds (memory size x execution time).

2. Step 2: Match correct units

   Requests count how many times function runs; GB-seconds measure memory used over time.

3. Final Answer:

   Number of requests and GB-seconds -> Option C

4. Quick Check:

   Requests + GB-seconds = pricing units [OK]

Hint: Think requests and memory-time units [OK]

Common Mistakes:

• Using CPU cycles or network packets incorrectly
• Confusing storage with compute time
• Mixing units like MB with packets

3. If a Lambda function runs 1,000,000 times with 512 MB memory for 1 second each, which factor mainly increases the cost?

medium

A. Execution time of 1 second per request

B. Network bandwidth used by the function

C. Memory size doubling from 256 MB to 512 MB

D. Number of requests being 1,000,000

Solution

1. Step 1: Understand cost components

   Cost depends on requests and GB-seconds (memory size x execution time x requests).

2. Step 2: Analyze impact of memory size

   Doubling memory from 256 MB to 512 MB doubles GB-seconds, increasing cost significantly, but the number of requests (1,000,000) is the main driver of total cost.

3. Final Answer:

   Number of requests being 1,000,000 -> Option D

4. Quick Check:

   Requests x GB-seconds = total cost [OK]

Hint: Number of requests greatly impacts total cost [OK]

Common Mistakes:

• Ignoring number of requests effect
• Thinking network bandwidth affects Lambda cost
• Assuming execution time or memory alone drives cost

4. A developer notices their Lambda cost is higher than expected. They set memory to 1024 MB but function runs only 100 ms. What is the likely issue?

medium

A. Memory size is too high for short execution time

B. Number of requests is too low

C. Function execution time is too long

D. Free tier is not applied to this function

Solution

1. Step 1: Review memory and execution time relation

   Cost depends on memory size multiplied by execution time. High memory with short time still costs more than lower memory.

2. Step 2: Identify cost cause

   Setting memory to 1024 MB increases GB-seconds cost even if function runs only 100 ms.

3. Final Answer:

   Memory size is too high for short execution time -> Option A

4. Quick Check:

   High memory + short time can increase cost [OK]

Hint: High memory with short run still costs more [OK]

Common Mistakes:

• Assuming short execution time always means low cost
• Ignoring memory size impact
• Thinking free tier always applies

5. A company uses Lambda functions with 256 MB memory running 200 ms per request. They want to reduce cost without changing code. Which approach helps most?

hard

A. Switch to EC2 instances for better pricing

B. Reduce memory size to 128 MB if function still runs correctly

C. Increase number of requests to use free tier fully

D. Increase memory size to reduce execution time

Solution

1. Step 1: Understand cost relation to memory and time

   Cost = requests x memory size x execution time. Reducing memory lowers GB-seconds cost if function still works.

2. Step 2: Evaluate options

   Reducing memory to 128 MB saves cost if performance is acceptable. Increasing memory or requests raises cost. Switching to EC2 is a different model and may not be cheaper.

3. Final Answer:

   Reduce memory size to 128 MB if function still runs correctly -> Option B

4. Quick Check:

   Lower memory reduces GB-seconds cost [OK]

Hint: Lower memory if function still works to save cost [OK]

Common Mistakes:

• Increasing memory without checking cost impact
• Thinking more requests reduce cost
• Assuming EC2 always cheaper than Lambda