Most of the stuff we used is based on some very boring tech. It may get upgraded to something fancy when the product/service scales to a significant number of u

Most of the stuff we used is based on some very boring tech. It may get upgraded to something fancy when the product/service scales to a significant number of users, but Spring+Postgres (or RoR, or Django, or PHP...) will get you there with no problems. Facebook was PHP, Instagram was Django etc. They became what they became while using incredibly boring "old-school" tech. The product is paramount, not the tech.