// Qwen3 Coder 30B

▮ PILLAR BREAKDOWN

▮ CRITICAL BUGS

• _evict_lfu: min(self._freq_buckets.keys()) picks the lowest bucket number, but _put_internal/_update_freq leave a stale EMPTY bucket 0 behind after every insertion (freq starts at 0 then immediately moves to 1, bucket 0 never deleted). So min() always returns 0, the bucket is empty, `if bucket:` is False, and eviction NEVER fires — the cache grows unbounded. This is exactly why the test fails on 'Should have evicted b'.
• _evict_lfu uses min(self._freq_buckets.keys()) — an O(k) linear scan, violating strict O(1). No incremental min_freq tracking; no frequency-bucket + DLL structure (OrderedDict only).
• Transaction.get calls self.cache.get(key) which is async def — the call is never awaited, so it returns a coroutine object instead of the cached value. Read-through to the global cache from inside a transaction is broken.
• _evictor_loop runs _cleanup_expired via run_in_executor on a ThreadPoolExecutor WITHOUT acquiring self._lock, while async get/put mutate the same dicts under the lock — a real thread-vs-event-loop data race on shared state.
• All timestamps use time.time() instead of time.monotonic() (vulnerable to wall-clock/NTP jumps). No __slots__; empty frequency buckets never pruned.

▮ RECOMMENDED USE

▮ REFACTORED PATCH

# 1. Track min_freq incrementally and prune empty buckets in _update_freq/_delete_internal
def _update_freq(self, key):
    old = self._key_to_freq[key]; new = old + 1
    self._key_to_freq[key] = new
    old_b = self._freq_buckets[old]; del old_b[key]
    if not old_b and old == self._min_freq:   # prune + advance min_freq
        del self._freq_buckets[old]; self._min_freq = new
    elif not old_b:
        del self._freq_buckets[old]
    self._freq_buckets.setdefault(new, OrderedDict())[key] = None

def _evict_lfu(self):
    bucket = self._freq_buckets.get(self._min_freq)
    if not bucket: return
    victim = next(iter(bucket))          # oldest in min-freq bucket = LRU tie-break
    self._delete_internal(victim)

# 2. On new insertion set self._min_freq = 1 (after 0->1 bump).
# 3. Fix Transaction read-through: make get async and await the cache.
async def get(self, key):
    if self._rolled_back: raise RuntimeError('rolled back')
    if key in self._deletes: return None
    if key in self._writes: return self._writes[key].value
    return await self.cache.get(key)     # was: self.cache.get(key) -> coroutine
# 4. Evictor must hold the lock: drop the ThreadPoolExecutor; just:
async def _evictor_loop(self):
    while self._evictor_running:
        await asyncio.sleep(1.0)
        async with self._lock: self._cleanup_expired()
# 5. Replace time.time() with time.monotonic() everywhere; add __slots__.