Letters of recommendation only from employers and managers I am looking to apply for a professional masters program in computer science (M.E. in Computer Science). This program is designed to for the working software engineer and thus not advised for those interested in doing computer science research in academia.  As part of this, I am going to need to submit 3 letters of recommendation. It has been a few years since I graduated with my bachelors and I did not have a significant relationship with any of the professors in my undergraduate program. Thus, I would not be comfortable asking them for a letter of recommendation.

I am now working and I am highly regarded at work. I am confident that I could get very strong letters from various managers that I have worked with at my company. Will 3 strong letters of recommendation from these individuals be enough? How will they be weighed against a less strong letter from an undergrad professor?
I have only been an admission committee member in the biomedical field so I cannot say too much about your field. For us, here are the concerns.

Generally, the pattern we have seen is applicants who returned to school after a long period working in industry face a harder time. A few factors include age difference (harder to find study partners), technology gap (unfamiliar with online learning platform or software), and anxiety related to assessment (examinations, tests, etc.)

While I understand it's a professional degree, a professional degree is still a degree given in an educational organization. There will be assignments, due dates, evaluation, course load management, study skill application, group work, etc. It will not be free of academic features. Admission committee would like to know if the applicants are ready for that.

If you have had a strong relationship with any professor I'd recommend go get his/her letter that would highlight your abilities as a student, but too bad you haven't had one or it may be too long a gap. This is not to say you should give up one strong co-worker's reference letter in favor of a weaker one from a former professor. Instead, a second best approach would be to ask one of your reference persons (preferably the one who trained you or someone who holds an adjunct professor title elsewhere) to highlight your good properties as a learner, and (if he/she also teaches) provide an estimation on your ability to thrive in an academic environment.

Another possible step to take is to ask the admission/recruitment staff. They can perhaps also let you know what the general patterns are and if your combination of reference letters would raise a red flag.

Good luck!