i have seen many posts about mvp and narrowing scope here--all right on the money.
some other things that have worked for me, i'm the world's biggest procrastinator and i have literally 20-30 side projects that i've started for some time, was extremely passionate about, and then moved onto the next big thing, but i've recently had a few projects that i went deep on and actually got out, even hoping to build a business out of.
i've also found that the technology stack is not that critical, as a perfectionist i want to create a kickass platform that's easily maintainable, beautifully coded, using all the right tools that can meet billions of requests per day from the start, easy to deploy, automated, etc, but that typically just leads me down a huge rat hole. if your energy is finite (for me it is), you should focus all of it on getting your stuff out the door as quickly as possible, getting it in front of potential users because often times what you think is a great idea is raw and will need tuning. make things functional, able to showcase your main idea (or a particular use case), don't have to have all use cases fully done. get it out there and iterate. i'm certain that there are people that can make all the right technology decisions from the get go to support billions of requests per day, fully automated (if you are one of these, please email me right away!) but you're solving the wrong problems, if you want to get a side project or business out there, go build it, get it out there and then iterate, and iterate fast.
for the sake of argument, probably side projects like tools or libraries, these are a bit different in nature, you probably want to choose the right technology stack, etc. but if you want to build a business out of your side project, then don't dwell on this too much, use what you're familiar with that can give you the quickest turnaround, there will be pains with whichever tech stack you choose, some more than others, but it will pale in comparison to the roadblocks in front of you to build something into a business.
for one of my recent projects, i use sqlite3 for my relational database, i don't even want to spend all the 30 minutes or whatever to set up postgresql, it's to that level of scope reduction. when users grow, then i'll spend the time to upgrade and add backups, etc.