It depends on your experience and career trajectory. You have a lot of firm specific knowledge, which makes you more valuable to the firm but if you're using an internal stack maybe the only people who value that knowledge are the company you're working for. That's a bad bargaining position. And if you've been at the same company for nine years and have not been negotiating aggressively for raises the whole time there's an excellent chance you're underpaid because job hopping every two years is really the only semi-reliable way to get a 20% raise.
Try interviewing and seeing what you get offered.