Least connections sends requests to the server with fewest active connections.
How it works:
Track active connections per server
New request goes to server with lowest count
Increment on assignment, decrement on completion
Pros:
- Adapts to varying request durations
- Naturally handles slow servers (they accumulate connections)
Cons:
- Requires connection tracking state
- Does not account for server capacity
Better than round robin for heterogeneous workloads.