The concept of 'storing a map as JSON' in a serverless context usually translates to saving or reading a file in a bucket, like S3 or GCS, but then again, this brings us back to waste time installing and managing an SDK.
Got your point, and for larger projects, a more structured approach definitely makes sense. However, I often find myself needing something like this, so I went ahead and built it.
I get that not everyone wants to install packages and SDKs or look up the two or three lines of code needed to save a file to S3. But if you do need real data storage, or everything a real server can provide, I think it's good to know how to do that. I think starting with serverless is like starting with instant microwave meals -- you get stuck with low-quality and high-cost food and never learn how to cook.
Seriously, if you can't install redis or something just like it, or just store a map as JSON in a file and read that, you can't call yourself a programmer.