Building a modern Software as a Service platform brings a lot of interesting engineering challenges. During this talk, I’m going to share my team’s journey of building a SaaS from scratch in 2020. First, we are going to start with the technologies and the architecture we picked. Then, we’ll go over the interesting challenge of implementing multitenancy. And we'll see how we benchmarked three different options and picked one. And last but not least, we’ll explore how every startup can use open source technologies to build observability infrastructure. And how to run their SaaS in production.