May I be employed in the public sector after retirement?

Yes, although the amount that a retiree who is receiving a retirement allowance can earn for performing services in the public sector in Massachusetts is limited, as are the hours that the retiree can be employed in the public sector. A retiree can be employed in the public sector in Massachusetts for not more than 1,200 hours in a calendar year. The earnings from this employment when added to the retirement allowance cannot exceed the amount currently being paid to the position from which the retiree retired, plus $15,000. This limitation applies to all retirees receiving an allowance from a public retirement system in Massachusetts. There are some exceptions to this limitation, for example payments for service in an elected office after retirement. A person who has retired for superannuation (as opposed to a disability retiree) can be employed in the private sector or in the public sector in another state without limitation. Upon retirement, All retirees receive a memorandum summarizing future employment.

https://www.mass.gov/guides/working-receiving-a-public-retirement-benefit