Ask HN: Learning material for data design/architecture

I worked for a large cooperation where senior engs. would design the overall layout of our services, and we (junior) focused on implementation. Now I work at a startup and am involved design decisions. Therefore, I would like to learn about software design and architecture. About the application, we are medium-sized company and in a range where computations could run on a local machine (no-big data) but the data themselves can vary a bit from customer to customer.