So you need to consider this a very large equation, and it involves your value to the company compared to their value to you. So let's look at the right side:

So you need to consider this a very large equation, and it involves your value to the company compared to their value to you. So let's look at the right side: their value to you. Do you need the money? Do you have a family to support? Can you find another job quickly in {your city here}, or are you senior and need more time? If you quit, can you coast on savings and credit until you find something else? Do you think it's easier to find a job in your market while employed or unemployed? If you search while working, can you pull it off without tipping off your coworkers? These things will determine how quickly you can bail and find new work if you decide you don't want this job. Now let's look at left side. If you say no, can the company replace you quickly? Can the job be handed to the guy in the next cube, marking you as redundant? Do you have some special business knowledge and/or talent that can't be replaced quickly? (An aside: Remember, ABOVE ALL, that everyone is replaceable given enough money and time so you should be continuously aware of what value your company places on you. That is a career skill you need forever, so learn it quickly. Know when it's time to jump and when it's time to negotiate for better treatment.) Now compute the two sides out (it's never a perfect equality) and play the scenario in your head. You can certainly say no and the company can fire you on the spot or perhaps slowly work on replacing you without telling you. This is the absolute worst case for you. Being fired makes life a lot harder going forward and takes a long time to recover from. Perhaps the company is more sympathetic and will reconsider their order and find something different for you to work on. But don't count on it. Go with the worst-case scenario and think it through. We've all had assignments we don't want to do, it comes with the business. Don't think if you move to a new company it won't happen again. Sometimes you need to excel on sucky gruntwork projects to get trusted with the shiny nice and fun ones, especially if you are young and/or new to the company. Perhaps having extensive experience on the frontend will supremely qualify you for the backend work later. We used to call this "paying your dues". Good luck.