I'm a software developer on a team of five people. This team has a lead, a web developer, a back-end developer, and two mobile developers. This team structure is relatively new, and we are currently working on our second major project.
I was hired as an iOS developer. A few months ago, I voluntarily took up a few days' worth of back-end work when the usual person for that was too busy, and I had no major iOS work on my plate at the time. My team lead was impressed that I stepped up and I was given a small raise by our department head shortly after. I've since occasionally stepped in to do very minor back-end work when needed.
When my team started the current project (a major new feature in our product), the lead assigned me to all iOS work (as expected), but also all back-end work. I'm not sure why. Our back-end developer is busy working on an unrelated tech debt issue, but the lead formerly worked on the back-end and knows the code base much better than I do. He doesn't seem to be working on implementing any part of this project at all and I think he could be pulling more weight.
Now I'm in a stressful situation because I'm still working on the back-end and I haven't had time to do any iOS work, so the feature is far behind on iOS compared to web and Android. To be clear, I don't mind being assigned back-end work occasionally, but in hindsight this has been way too much for me to take on.
This is partially my fault for not raising any concerns when I was assigned all of this work. I've only been in the workforce for a little over a year and I've been trying not to be a squeaky wheel.
Now that the back-end work is almost done, I don't think it's worth trying to change course for this project. However, I do want to communicate to my lead that I don't want to be put in this position again. I want to focus on primarily iOS work going forward, as that's what I was hired for.
I'm worried that my lead thinks the raise I accepted implicitly changes my job responsibilities. I also don't want to sound like I'm accusing my lead of not pulling his weight. How should I ask not to be assigned large amounts of non-iOS work in the future?