diff --git a/api/advent22_api/core/dav/dec.py b/api/advent22_api/core/dav/dec.py
new file mode 100644
index 0000000..116122c
--- /dev/null
+++ b/api/advent22_api/core/dav/dec.py
@@ -0,0 +1,115 @@
+import inspect
+from base64 import urlsafe_b64encode
+from collections.abc import Callable
+from dataclasses import dataclass
+from functools import wraps
+from itertools import chain
+from typing import Iterable, ParamSpec, TypeVar
+
+from redis import Redis
+
+
+@dataclass(frozen=True, kw_only=True, slots=True)
+class Config:
+    redis: Redis
+    prefix: str | None = "cache"
+    ttl_fresh: int = 600
+    ttl_stale: int | None = None
+
+
+def qualified_name(callable_obj) -> str:
+    # callable classes/instances
+    if hasattr(callable_obj, "__call__") and not inspect.isroutine(callable_obj):
+        # callable instance: use its class
+        cls = callable_obj.__class__
+        module = getattr(cls, "__module__", None)
+        qual = getattr(cls, "__qualname__", cls.__name__)
+        return f"{module}.{qual}" if module else qual
+
+    # functions, methods, builtins
+    # unwrap descriptors like staticmethod/classmethod
+    if isinstance(callable_obj, staticmethod | classmethod):
+        callable_obj = callable_obj.__func__
+
+    # bound method
+    if inspect.ismethod(callable_obj):
+        func = callable_obj.__func__
+        owner = getattr(func, "__qualname__", func.__name__).rsplit(".", 1)[0]
+        module = getattr(func, "__module__", None)
+        qual = f"{owner}.{func.__name__}"
+        return f"{module}.{qual}" if module else qual
+
+    # regular function or builtin
+    if inspect.isfunction(callable_obj) or inspect.isbuiltin(callable_obj):
+        module = getattr(callable_obj, "__module__", None)
+        qual = getattr(callable_obj, "__qualname__", callable_obj.__name__)
+        return f"{module}.{qual}" if module else qual
+
+    # fallback for other callables (functors, functools.partial, etc.)
+    try:
+        module = getattr(callable_obj, "__module__", None)
+        qual = getattr(callable_obj, "__qualname__", None) or getattr(
+            callable_obj, "__name__", type(callable_obj).__name__
+        )
+        return f"{module}.{qual}" if module else qual
+
+    except Exception:
+        return urlsafe_b64encode(repr(callable_obj).encode("utf-8")).decode("utf-8")
+
+
+P = ParamSpec("P")
+R = TypeVar("R")
+
+
+def args_slice(func: Callable[P, R], *args: Iterable) -> tuple:
+    if hasattr(func, "__call__") and not inspect.isroutine(func):
+        return args[1:]
+
+    if isinstance(func, staticmethod | classmethod):
+        func = func.__func__
+
+    if inspect.ismethod(func):
+        return args[1:]
+
+    return tuple(*args)
+
+
+def redis_cached(cfg: Config) -> Callable[[Callable[P, R]], Callable[P, R]]:
+    """ """
+
+    def cache_key(func: Callable[P, R], *args: P.args, **kwargs: P.kwargs) -> str:
+        """Return a cache key for use with cached methods."""
+
+        kwargs_by_key = sorted(kwargs.items(), key=lambda kv: kv[0])
+
+        parts = chain(
+            (qualified_name(func),),
+            # positional args
+            (repr(arg) for arg in args_slice(func, args)),
+            # keyword args
+            (f"{k}={v!r}" for k, v in kwargs_by_key),
+        )
+
+        if cfg.prefix is not None:
+            parts = chain(
+                (cfg.prefix,),
+                parts,
+            )
+
+        return ":".join(parts)
+
+    def decorator(func: Callable[P, R]) -> Callable[P, R]:
+        """ """
+
+        @wraps(func)
+        def wrapper(*args: P.args, **kwargs: P.kwargs) -> R:
+            key = cache_key(func, *args, **kwargs)
+
+            # pre-hook
+            result = func(*args, **kwargs)
+            # post-hook
+            return result
+
+        return wrapper
+
+    return decorator