Lambda pricing model in AWS - Step-by-Step Execution

Process Flow - Lambda pricing model

Request triggers Lambda

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Count number of requests

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Measure execution duration

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Calculate GB-seconds used

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Apply free tier if eligible

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Calculate cost based on requests + duration

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Generate billing amount

This flow shows how AWS Lambda pricing is calculated step-by-step from requests and execution time to final billing.

Execution Sample

AWS

Requests = 3,000,000
Duration = 200 ms
Memory = 512 MB

Calculate GB-seconds and cost

Calculates cost for 3 million Lambda requests with 200 ms duration and 512 MB memory.

Process Table

Step	Metric	Value	Calculation	Result
1	Requests	3,000,000	Count total requests	3,000,000
2	Duration per request	200 ms	Given	0.2 seconds
3	Memory allocated	512 MB	Given	0.5 GB
4	Total compute (GB-seconds)	3,000,000 * 0.2 * 0.5	3,000,000 * 0.1	300,000 GB-seconds
5	Free tier requests	1,000,000	Subtract free tier	2,000,000 billable requests
6	Free tier compute	400,000 GB-seconds	Subtract free tier	300,000 - 400,000 = 0 (free tier covers all)
7	Billable compute	0	No charge for compute	0 GB-seconds
8	Request cost	2,000,000	2,000,000 / 1,000,000 * $0.20	$0.40
9	Compute cost	0 GB-seconds	0 * $0.0000166667	$0.00
10	Total cost	-	$0.40 + $0.00	$0.40

💡 Free tier covers all compute usage; only requests beyond free tier are charged.

Status Tracker

Variable	Start	After Step 4	After Step 6	Final
Requests	3,000,000	3,000,000	2,000,000	2,000,000
Duration (seconds)	0.2	0.2	0.2	0.2
Memory (GB)	0.5	0.5	0.5	0.5
Compute (GB-seconds)	N/A	300,000	0	0
Request Cost ($)	N/A	N/A	N/A	0.40
Compute Cost ($)	N/A	N/A	N/A	0.00
Total Cost ($)	N/A	N/A	N/A	0.40

Key Moments - 3 Insights

Why is the compute cost zero even though there is compute usage?

Because the free tier includes 400,000 GB-seconds, which covers the 300,000 GB-seconds used (see step 6 in execution_table). So no compute charges apply.

Why do we subtract 1,000,000 requests in step 5?

AWS Lambda offers 1 million free requests per month. We subtract this free tier from total requests to find billable requests (step 5).

How is the total compute (GB-seconds) calculated?

Multiply number of requests by duration in seconds and memory in GB (step 4). Here: 3,000,000 * 0.2 * 0.5 = 300,000 GB-seconds.

Visual Quiz - 3 Questions

Look at the execution_table at step 4. What is the total compute in GB-seconds?

A 600,000

B 300,000

C 150,000

D 3,000,000

💡 Hint

Check the 'Result' column in step 4 of execution_table.

At which step does the free tier reduce the billable compute to zero?

A Step 6

B Step 5

C Step 7

D Step 8

💡 Hint

Look for where compute usage is adjusted by free tier in execution_table.

If the number of requests was 500,000 instead of 3,000,000, what would be the billable requests?

A 500,000

B 1,000,000

C 0

D 2,000,000

💡 Hint

Refer to step 5 where free tier requests are subtracted from total requests.

Concept Snapshot

AWS Lambda pricing is based on two parts:
- Number of requests (first 1M free, then $0.20 per million)
- Compute time in GB-seconds (memory GB * execution seconds)
Free tier covers 1M requests and 400,000 GB-seconds monthly.
Charges apply only beyond free tier.
Calculate total cost = request cost + compute cost.

Full Transcript

AWS Lambda pricing works by counting how many times your function runs and how long it runs with how much memory. Each request counts, and each second of execution with allocated memory counts as GB-seconds. AWS gives you a free tier of 1 million requests and 400,000 GB-seconds per month. You pay only for what you use beyond that. For example, if you run 3 million requests with 512 MB memory and 200 ms duration, you calculate total GB-seconds by multiplying requests, duration in seconds, and memory in GB. Then subtract free tier amounts. The remaining billable requests and compute are multiplied by their rates to get the total cost. This step-by-step calculation helps you understand your Lambda bill clearly.