How can I maintain interest in work after being at the same company for over a year?

The initial year, everything is new and you are challenged and learning. From your previous experiences, what do you think draws your to starting a new job, and being in that initial phase?

Is it the steep learning curve? Is it the challenge? It is natural that things start to settle on that one year mark, you are familar with the code base, people and the pace.

I would recommend, you talk to your manager find ways that you can contribute to a brand new project that your team has? That way you can maintain the excitement of being part of something new without having to switch jobs.

The fact that you're bored is a good sign, that means you're probably competent in your role.

So, it's probably time to tackle harder problems. Expanding your role to handle more aggressive refactors, be involved in more of the product design process, building internal / developer tools, and mentoring others are all great problems and domains to learn more and add some positive stress.

If you have a good manager, let them know and they will be happy to give you harder work. If your manager is not as helpful, then you get to talk to coworkers and other teams to identify problems yourself and take away time from your regular responsibilities to work on these. If your bored and can manage expectations, it will be easy for you to manage your ambitious learning and your regular day to day.