If speed is your biggest concern, it is likely that you will build a system that has a lot of services which each have a shallow stack. Each service would not go very deep into the service stack before hitting the data it was looking for. PHP, for example, almost always works this way. Maybe the data would be in a cache, as suggested by other commenters here. You have more places to put caches if you think about your system as multiple services.

If you are making a big system, you probably would not want to try to put all of the components in one monolithic place. I argued that this makes testing and release more complicated (and slower). But, I suspect it also affects runtime speed by making the stack deeper. You would be doing more switching to get your requests to the right components.