>Then one weekend we tripled our userbase and horizontally scaling required massive changes in database architecture, sharding solutions, etc.
You took the short easy route out of the gate instead of building for what you were planning to handle. This is the opposite of what I espouse. If you were going about it my way, you build that in from the ground up. Harder and a bit bumpier to roll out from the get go, but has worked well for me in the past.
If you want to spend capital for an unpredictable eventuality that may never pass over taking advantage of another company's investment to scale cost... sure, that's definitely the hard route.
I wouldn't call it "good" or "intelligent", but it's definitely hard.
You took the short easy route out of the gate instead of building for what you were planning to handle. This is the opposite of what I espouse. If you were going about it my way, you build that in from the ground up. Harder and a bit bumpier to roll out from the get go, but has worked well for me in the past.