Meta AI Open-Sources Rebalancer: A C++ Assignment Solver That Runs About 40 Million Placement Problems a Day

What happened

The release ships under Apache 2.0 with documentation , a PyPI package and a debugging UI called Rebalancer Explorer. Meta has open-sourced Rebalancer, the C++ and Python library it has used for over 9 years to place shards, servers and traffic.

It handles about 40 million assignment problems a day, using local search or MIP solvers like Gurobi, FICO Xpress and HiGHS. Meta has open-sourced Rebalancer , a C++ library with a Python interface for solving assignment problems.

It decides which objects go into which bins under constraints and objectives. According to the Engineering at Meta’s post , Rebalancer has handled resource allocation across Meta for over 9 years.