Comment by mjr00

> The first problem every startup should solve is “how do we have enough money to not go bust in two months”, but that’s a hard problem, whereas scalability is trivially solvable by reading a few engineering blogs [...] Do you know what the difference between Google and your startup is? It’s definitely not scalability, you’ve solved that problem. It’s that Google has billions upon billions with which to pay for that scalability, which is really good because scalability is expensive.

Too true. Now that I've stepped into an "engineering leadership" role and spend as much time looking at finances as I do at code, I've formed the opinion that in 99.999% of cases, engineering problems are really business problems. If you could throw infinite time and money at the technical challenges, they'd no longer be challenging. But businesses, especially startups, don't have infinite (or even "some") money and time, so the challenge is doing the best engineering work you can, given time and budget constraints.

> The downsides [of the monolith approach]

I like the article's suggestion of using explicitly defined API boundaries between modules, and that's a good approach for a monolith. However one massive downside that cannot be ignored -- by having a single monolith you now have an implicit dependency on the same runtime working on all parts of your code. What I mean by this is, all your code is going to share the same Python version and same libraries (particularly true in Python, where it's not a common/well-supported use case to have multiple versions of library dependencies). This means that if you're working on Module A, and you realize you need a new feature from Pandas 2.x, but the rest of the code is on Pandas 1.x... well, you can't upgrade unless you go and fix Modules B, C, D ... Z to work with Pandas 2.

This won't be an issue at the start, but it's worth pointing out. Being forced to upgrade a core library or language runtime and finding out it's a multi-month disruptive project can be brutal.