I have joined a new company and the original, sole developer of an e-commerce site has left the country (talk about key-man dependency) so I've had to come in and take over.

Luckily the code is written quite nicely and so I've been able to maintain it and extend.

We run the site as a monolith (which is fine for its size) and only one instance of the site exists on a single EC2 instance.

I'm pretty much new to AWS, and in previous firms we've had Operations teams to sort the infrastructure side, but recently spikes in traffic have brought our site down.

I've told the manager we could load-balance the site, or preferably use something like ElasticBeanstalk to abstract a LOT of the infrastructure away, and have it auto-scale our app as load increases.

I think I've got buy-in to do this, but my main fear is because we have no integration/unit tests, and the original developer is long-gone - I'm not sure what "checklist" I should score our site against in order to make sure it won't have strange behaviour once load balanced.

It uses IdentityFramework, and I think a lot of user-based information (i.e. shopping cart, culture/currency) are stored in Session variables (stored in a cookie).

We don't have any logging but I am going to introduce SQL logging anyway, so that it should be one central repository.

AFAIK there are no user-uploaded images that are stored on the filesystem, but if there are I can re-write the code to point to S3 hopefully.

Is there any such guide to how to make sure a site will work once load-balanced - and any test plans I should look to execute e.t.c.?

Thanks !

TL;DR -> want to load balance .NET Core site, scared that things will break because of server-specific dependencies. what is the protocol for preparing a site for load-balancing