My second professional rule is that when I stop learning, it's time to move on. I always want to challenge myself. If I'm not challenging myself, I'm not improving and, like you, I get bored.
I don't know a lot about your situation, nor do I have an inkling of your capabilities. That said, it sounds like your situation doesn't satisfy either of my two rules. If that's the case, I recommend you look around for something new, where you can find people that will push you to be better.
That said, there are other options. You may find that teaching others is a rewarding experience. Perhaps a more engaging social life will mitigate boredom at the day job. You may find that having some side projects can invigorate your interest. Or perhaps digging into another language or new technology can help keep you interested in your job.
You say you've got a lot of experience on the back-end. Maybe another step would be investigating more DevOps type roles. Implement containers and autoscale, automate deployments, build a CI server. Or look into starting a professional development group at work to teach or learn new skills. Ask directly for feedback. If nobody is offering, ask them. Offer to take on new responsibilities. Identify some pain point that the company has and solve it. It might lead to opportunities to grow the team.
If you're bored for too long, you're going to be miserable. The only way to fix boredom is to seek out change, whether that means a new job or a new skill or new friends. Unfortunately, this is a very, very common scenario out there. The good news is that it is entirely within your power to fix.
Good luck.