The topos module got major refactoring in the master branch (to have support for other backends, redis (see topos_redis) being the one added along with the old support for db). I am not sure these patches can be backported without a consistent work. If someone does it and makes a pull request for branch 5.0, I will review and merge it. But I do not have the time at this moment. In few week 5.1 will be out anyhow as a stable release, my efforts on spare time are directed to make it stable.