See this

https://ask.fedweek.com/federal-retirement/retirement-eligibility/

Under CSRS/CSRS Offset, and employee may retire at age 62 with five years of service, 60 with 20, or 55 with 30.

Under FERS, an employee who meets one of the following age and service requirements is entitled to an immediate retirement benefit: age 62 with five years of service, 60 with 20, minimum retirement age (MRA) with 30 or MRA with 10 (but with reduced benefits).

Minimum Retirement Age
If you were born	Your MRA is
Before 1948	55
1948	55 and 2 months
1949	55 and 4 months
1950	55 and 6 months
1951	55 and 8 months
1952	55 and 10 months
1953 - 1964	56
1965	56 and 2 months
1966	56 and 4 months
1967	56 and 6 months
1968	56 and 8 months
1969	56 and 10 months
1970 and after	57