Lambda pricing model in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding AWS Lambda Pricing Components

Which of the following factors directly affect the cost of running an AWS Lambda function?

A The number of requests and the duration of each execution measured in milliseconds.

B The size of the deployment package and the number of environment variables used.

C The number of concurrent executions and the size of the Lambda function's memory allocation.

D The AWS region and the number of API Gateway endpoints connected.

💡 Hint

Think about what AWS charges for when you invoke a Lambda function.

AWS Lambda pricing is based on the number of requests and the duration of execution, which depends on the allocated memory and execution time. The deployment package size and environment variables do not affect pricing directly.

❓ service_behavior

intermediate

Effect of Memory Allocation on Lambda Cost

You have a Lambda function that runs for 1 second. You increase its memory from 128 MB to 512 MB. How does this change affect the cost per invocation?

A The cost per invocation doubles because memory increased four times but duration halves.

B The cost per invocation stays the same because duration is unchanged.

C The cost per invocation quadruples because memory increased four times.

D The cost per invocation increases linearly with memory size and duration.

💡 Hint

Remember that cost depends on both memory size and execution time.

Cost is calculated as memory size (in GB) multiplied by execution duration (in seconds). Increasing memory from 128 MB to 512 MB is a 4x increase, so cost per invocation quadruples if duration stays the same.

❓ Architecture

advanced

Optimizing Lambda Cost with Execution Duration

You have a Lambda function that processes data in 2 seconds with 256 MB memory. You optimize the code to run in 1 second but need 512 MB memory to do so. What is the impact on cost per invocation?

A Cost remains the same because duration halves and memory doubles.

B Cost doubles because memory doubles despite duration halving.

C Cost halves because duration halves despite memory doubling.

D Cost quadruples because memory doubles and duration halves.

💡 Hint

Calculate cost as memory size times duration.

Cost = memory (GB) * duration (seconds). Doubling memory and halving duration results in the same cost.

❓ security

advanced

Impact of Lambda Provisioned Concurrency on Pricing

Which statement correctly describes how enabling Provisioned Concurrency affects AWS Lambda pricing?

A Provisioned Concurrency only affects cold start times and does not change pricing.

B You pay a fixed hourly rate for the provisioned concurrency plus the usual request and duration charges.

C Provisioned Concurrency eliminates duration charges but increases request charges.

D Provisioned Concurrency replaces the request charges with a flat monthly fee.

💡 Hint

Think about what extra resource is reserved when you enable Provisioned Concurrency.

Provisioned Concurrency reserves execution environments, so you pay an hourly fee for that reservation in addition to normal request and duration charges.

✅ Best Practice

expert

Choosing Memory Size for Cost Efficiency

You want to minimize AWS Lambda cost for a function that runs variable workloads. Which approach best balances cost and performance?

A Set memory to the lowest possible value to minimize cost per millisecond, accepting longer execution times.

B Set memory high enough to reduce execution time significantly, even if cost per millisecond is higher.

C Randomly adjust memory size and monitor costs without analyzing execution time.

D Use a memory size that results in the lowest total cost, considering both memory and execution time together.

💡 Hint

Think about total cost = memory size * execution duration.

The best practice is to find the memory size that minimizes the product of memory and execution time, not just the lowest memory or fastest execution alone.