The main memory DBMS (MMDBMS) efficiently supports various database applications that require high performance since it employs main memory rather than disk as a primary storage. In this paper, we discuss the experiences obtained in developing the index manager of the Tachyon, a next generation MMDBMS. An index manager is an essential sub-component of a DBMS used to speed up the retrieval of objects from a large volume of a database in response to a certain search condition. Previous research efforts on indexing proposed various index structures. However, they hardly dealt with the practical issues occurred in implementing an index manager on a target DBMS. In this paper, we touch these issues and present our experiences in developing the index manager of the Tachyon as solutions. The main issues touched are (1) compact representation of an index entry, (2) support of variable-length keys, (3) support of multiple-attribute keys, (4) support of duplicated keys, (5) definition ..