Programmers are, by and large, quite bad at not breaking encapsulation when they're dealing with a monolith. Not their fault, really, but when management comes to you and says, hey, can't you get it done in just a day, we really need this, and you know you could if you just hacked through that particular isolation barrier just this once, and yeah it will create bad bugs if things change in a particular way in the future, but you'll leave a comment so it will be fine and this way you can go home and have an ipa and finish re-runs of that show you like so you break the rules just this once. And that only happens a few more times, and then slowly bit by bit things become intertwined and rigid, and then five years down the road when half the people have left and the team has grown and other teams use the project and are trying to commit code to it you have to go to management, hat in hand, sorry, we need to rewrite it from scratch to keep adding features, new and exciting and unexpected things happen when we change things in the current project.

Independent services that create a coherent whole enforce isolation barriers. I don't believe in microservices. These things don't need to be micro. They can be just normal-sized services. I don't even particularly care internal to those barriers how bad things get. There are programmers that write shit I think is hot garbage and will cause all kinds of bugs as time goes on. But if they are confined to their space space, and they're solving their problem and are happy and making management happy then w/e. That piece of the whole will collapse and die eventually, but it won't take everything with it. It's just a piece, and it provided value for a while, so probably worth it from a business sense.

But when you have a monolith? And Developer Dave and Programmer Pete tell Big Boss Bob that they could sure get that feature out quick if only it weren't for those pesky rules preventing them from putting in a few mutexes in that one module so they can just read some data directly from it, and boy wouldn't it that be swell? Well Big Boss Bob says we need to get this feature SHIPPED BOYES so buckle up and put in those mutexes, and now the fucking thread goes into a deadlock state every so often but it's really intermittent so you spend hours debugging the damn things and late nights because yeah features gotta ship but shit gotta work, and you trace it back to Developer Dave and Programmer Pete and their change but what do you do? Big Boss Bob said do it that way and what? You gonna whine to Director Dan about it? Is that gonna get you back your late night spend figuring out what was going on? Nah.

Make systems that are just small that when people break them completely it doesn't mean the end of the world to throw it out and start over.