Replacing a massive cron server

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To clarify a couple of things: AWS Lambda is one of many ways to deploy code on AWS. AWS Lambda ECS EC2 EKS etc... You can deploy almost any type of code on all of these including a python API. What makes AWS Lambda special is: You can deploy docker containers, or .zip files. LINK It is 100% "serverless", AKA AWS manages the server for you, and you just tell AWS how many instances you want to run. This is done with Firecracker LINK It can scale from 0-10,000+ instances really quickly It can be very cheap vs a EC2 instance if you have a bursty load You can string together multiple Lambda functions using AWS Step Functions LINK You can trigger the lambda functions with a wide range of things. LINK You can run numerous functions in parallel. Stateless (ish, you can have state, but don't do that) This is both positive and negative. Most modern code should be stateless. IE, you should be able to kill it at any point, and run it again. The state should be stored in a database, not locally with the code. AWS Lambda has some downsides: It can be expensive if you have a constant load Data processing, 5+ minute loads, etc. Most light/fast APIs will be much cheaper on Lambda than a tradition ECS + EC2 setup. Testing locally is annoying LINK Lambda does some weird things with requests. You need to add some middleware to handle it. LINK Cold starts! If you haven't called your Lambda in ~15 minutes, the next call can take much longer to start. LINK You don't have control, so if something goes wrong with AWS Lambda, you can't do anything about it. 15 minute max You can only keep a lambda up for a max of 15 minutes. For an API this is more than enough, but for a larger job you should look somewhere else (ECS Fargate, AWS Batch) Other limits (CPU, Time, RAM, etc.) LINK Other, more “traditional” ways to deploy a web API would be AWS ECS or AWS EC2. ECS offers something called Fargate. It is built on the same serverless framework (Firecracker) and will let you deploy code without dealing with the underlying hardware. This has a lot of the same advantages as AWS Lambda without most of the disadvantages. Now to the question I suspect you are really asking. "When should I use a Web API vs another processing method like a queue consumer, map reduce job, ETL pipeline, batch job, etc?" That is a very hard question to answer, and it depends on exactly what you are trying to do. Based on your post history, I assume you are trying to move a monolithic ERP system to microservices? EDIT: Sorry about the spam edits, I decided to move to my computer and give a better answer. More on reddit.com

Lambdas are likely going to be more expensive to run than containers if you have that many requests. The breakeven point depends on container you use, lambda memory and execution time, but generally it's in tens of millions requests per month. More on reddit.com

If you don't specify a VPC then the Lambda runs in an VPC internal to AWS managed by them. It runs in a public subnet with internet access and access to all AWS services. It's basically the best option unless your Lambda needs to talk to other resources within your own networks. More on reddit.com