At the end of the day, you just need to generate a PDF from a template. The template is a solved problem. Invoices generally do not have that huge amount of variability in terms of layout.
I have been using microinvoice (https://github.com/baptistejamin/node-microinvoice) for the past couple of months and it's been a breeze. It uses PDFKit underneathe and has been working really well. I don't think PDF generation is a task that should require using Chromium. There's pandoc & other libraries that can easily do this at a much lower cost to both resources and finance.
The blog posts sounds like its solving a problem that doesn't exist. Generating invoices _at scale_? Is scalibility really a problem here? Generating a PDF takes a couple of milliseconds. Rent a $5 VPS and it can generate all sorts of PDFs for you without an issue for a long time before you'd start worrying about scalability. Heck this sort of thing doesn't even need to be a dedicated service.
Not to downplay anyone's hard work but Lago just doesn't sound like it's solving a real problem.