Technical Engineering Blogs are important for a developer to know what and how engineering is done at scale.
Netflix TechBlog: Netflix has its own Technical blog where it shares how it is done inside Netflix. This blog is one of the best I've ever seen with so much quality content for backend engineers. Since Netflix is a video-streaming platform handling millions of requests simultaneously, the content is seen from that perspective which is a huge thing for developers. This blog covers topics like "How Netflix loads videos efficiently", "How movies are recommended to a user", "How thumbnails are chosen according to the user's watch history" etc...
Uber Engineering Blog: Uber is a transport company and everything in this blog relates to it. Similar to Netflix, but the domain changes. We can know the hurdles of a transport company at scale and also how do they handle them. Netflix Tech Blog has content on how streaming is done at scale, Uber has how transport is done at scale.
Slack Engineering Blog: Slack is a business communication platform. It has an active community of engineering blog team where they post their technical perspectives and how Slack has grown from scratch. It also covers topics like "How the codebase changes when a company like Slack grows". It is really interesting to see how powerful engineering has become.
Facebook Engineering Blog: Facebook tech blog covers engineering at Facebook for different platforms. Not just engineering, they also write technical content related to the products they own on Facebook. You can select from the web, ios, or android and read about their implementation.
Martin Fowler: Martin writes on different engineering topics ranging from coding techniques to system architecture. He has been writing for a long time and backend engineers like me try to squeeze as much content as possible from his posts.
Hacker News: It is not exactly a tech blog but a quality collection of news for the tech community. It a product of a famous startup incubator "Y Combinator". Simple UI and ever-updating of top posts make it a really useful website for developers.
Last but not the least, Mano Sriram writes on backend tech, system architecture, and distributed systems. So, make sure you follow him here 😉
The Engineering blogs mentioned above talks about how that particular company implements a technical piece. One can observe how that is implemented and built to get an idea of how things work at scale.