TimesTen was originally named as SmallBase and developed by HP Labs. Shortly after its first commercial use in 1995, the product was split out as a separate startup company and renamed as TimeTen. In 2005, the company with 90 employees at the time was acquired by Oracle. TimesTen was then integrated with Oracle software as well as services and become part of Oracle Database Products.
B+Tree Hash Table BitMap T-Tree
By default TimesTen uses B+Tree. The original version (SmallBase) from the 1990s supported T-Trees. TimesTen still supports T-Tree indexes but the administrator has to request for the DBMS to use them.
http://www.oracle.com/us/products/database/timesten/index.html
https://docs.oracle.com/database/timesten-18.1/
HP Labs
1996
SmallBase
Oracle