private Region findRegionByKeyWithoutLock(final byte[] key) {
        // return the greatest key less than or equal to the given key
        final Map.Entry<byte[], Long> entry = this.rangeTable.floorEntry(key);
        if (entry == null) {
            reportFail(key);
            throw reject(key, "fail to find region by key");
        }
        return this.regionTable.get(entry.getValue());
    }
Returns the list of regions to which the keys belongs.
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/client/RegionRouteTable.java