Well, you have a pretty good starting point. Since you work on the frontend, you should already have a pretty good idea of what an API takes as input and spits

Well, you have a pretty good starting point. Since you work on the frontend, you should already have a pretty good idea of what an API takes as input and spits out as output, so you already know what sort of data you need to work with on the backend. And assuming that you're fairly up to date with JavaScript, you basically already know a lot about how to work with Node.js, if that's the tool you want to learn. What kind of company do you work with? Do you have a backend engineer who you can approach and ask to mentor you? Express your interest in learning more about the backend and seeing if they can guide you through building some simple features entirely by yourself. You can start out with evaluating the spec you're given, building the backend, going over any feedback with them, and then using your frontend knowledge to finish that feature entirely yourself. Don't be discouraged about some of the complexity about databases and setting up complicated infrastructure: that can take a while to start to figure out. But if you can get an experienced backend engineer to help you with some of that tricky deployment/infrastructure stuff and just focus on the API you need to build, you can probably gain good experience through that. Of course, politics being what it is in some companies, a company who wants to restrict employees ambitions to keep them cheap and working for them without threat of being poached into a better role, or a backend engineer that is trying to protect some fiefdom, might give you some grief for thinking about stepping into something new. If your company isn't a help, a good potential option is joining a startup. In many cases, developers will have to wear multiple hats to try and get a new product off of the ground, so there might be an opportunity to take on some backend tasks there.