if (fromSize <= idealDataSizePerShardForZone) {
        return false;
    }

    if (toSize >= idealDataSizePerShardForZone) {
        // Do not use a shard if it already has more data than the ideal per-shard size
        return false;
    }

    if (fromSize - toSize < 3 * collDataSizeInfo.maxChunkSizeBytes) {
        // Do not balance if the collection's size differs too few between the chosen shards
        return false;
    }