Database Architecture and Partitioning Questions

import bisect
import hashlib

class ConsistentHashRing:
    def __init__(self, vnodes=100):
        self.vnodes = vnodes
        self.ring = []                # sorted list of vnode hashes (ints)
        self.hash2node = {}           # vnode_hash -> node_id

    def _hash(self, value):
        # stable 128-bit integer hash
        return int(hashlib.md5(value.encode('utf-8')).hexdigest(), 16)

    def add_node(self, node_id):
        for i in range(self.vnodes):
            vnode_key = f"{node_id}#{i}"
            h = self._hash(vnode_key)
            if h in self.hash2node:
                # extremely rare collision; skip or try alternate suffix
                continue
            bisect.insort(self.ring, h)
            self.hash2node[h] = node_id

    def remove_node(self, node_id):
        # remove all vnodes for this node
        to_remove = [h for h, n in self.hash2node.items() if n == node_id]
        for h in to_remove:
            idx = bisect.bisect_left(self.ring, h)
            if idx < len(self.ring) and self.ring[idx] == h:
                self.ring.pop(idx)
            del self.hash2node[h]

    def get_node_for_key(self, key):
        if not self.ring:
            return None
        h = self._hash(key)
        idx = bisect.bisect_right(self.ring, h)
        if idx == len(self.ring):
            idx = 0
        vnode_hash = self.ring[idx]
        return self.hash2node[vnode_hash]