diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4790ff1..c77b9fc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,8 +6,9 @@
 + Module `sqlalchemy`: 
     * removed deprecated alias `entity_base()`. use `declarative_base()` instead.
     * fix imports.
-+ Module `functools`: add `cooldown()`
++ Module `functools`: add `cooldown()`, `do_not_flood()`
 + Module `color`: add `ColorFormatter()`
++ Separated `suou[waiter]` dependency from `suou[quart]`
 
 ## 0.12.6
 
diff --git a/pyproject.toml b/pyproject.toml
index 5375510..0982b7e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -56,7 +56,9 @@ markdown = [
 ]
 quart = [
     "Quart",
-    "Quart-Schema",
+    "Quart-Schema"
+]
+waiter = [
     "starlette>=0.47.2"
 ]
 quart_auth = [
@@ -78,7 +80,8 @@ full = [
     "suou[quart_auth]", # includes quart, sqlalchemy and quart_sqlalchemy
     "suou[peewee]",
     "suou[markdown]",
-    "suou[sass]"
+    "suou[sass]",
+    "suou[waiter]"
 ]
 
 docs = [
diff --git a/src/suou/__init__.py b/src/suou/__init__.py
index 8b51746..fadb067 100644
--- a/src/suou/__init__.py
+++ b/src/suou/__init__.py
@@ -18,13 +18,14 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 
 from .iding import Siq, SiqCache, SiqType, SiqGen
 from .codecs import (StringCase, cb32encode, cb32decode, b32lencode, b32ldecode, b64encode, b64decode, b2048encode, b2048decode,
-    jsonencode, twocolon_list, want_bytes, want_str, ssv_list, want_urlsafe, want_urlsafe_bytes)
+    jsonencode, twocolon_list, want_bytes, want_str, ssv_list, want_urlsafe, want_urlsafe_bytes,
+    z85encode, z85decode)
 from .bits import count_ones, mask_shift, split_bits, join_bits, mod_ceil, mod_floor
 from .calendar import want_datetime, want_isodate, want_timestamp, age_and_days
 from .configparse import MissingConfigError, MissingConfigWarning, ConfigOptions, ConfigParserConfigSource, ConfigSource, DictConfigSource, ConfigValue, EnvConfigSource
 from .collections import TimedDict
 from .dei import dei_args
-from .functools import deprecated, not_implemented, timed_cache, none_pass, alru_cache, future
+from .functools import deprecated, not_implemented, timed_cache, none_pass, alru_cache, future, cooldown, do_not_flood
 from .classtools import Wanted, Incomplete
 from .itertools import makelist, kwargs_prefix, ltuple, rtuple, additem, addattr
 from .i18n import I18n, JsonI18n, TomlI18n
@@ -32,7 +33,7 @@ from .signing import UserSigner
 from .snowflake import Snowflake, SnowflakeGen
 from .lex import symbol_table, lex, ilex
 from .strtools import PrefixIdentifier
-from .validators import matches, not_less_than, not_greater_than, yesno
+from .validators import matches, not_less_than, not_greater_than, yesno, must_be
 from .redact import redact_url_password
 from .http import WantsContentType
 from .color import OKLabColor, chalk, WebColor, RGBColor, LinearRGBColor, \
@@ -40,7 +41,7 @@ from .color import OKLabColor, chalk, WebColor, RGBColor, LinearRGBColor, \
 from .mat import Matrix
 from .argparse import LetterSubparsers
 
-__version__ = "0.13.0a3"
+__version__ = "0.13.0a4"
 
 __all__ = (
     'ColorFormatter',
@@ -54,7 +55,7 @@ __all__ = (
     'WebColor', 'XYZColor',
     'addattr', 'additem', 'age_and_days', 'alru_cache', 'b2048decode', 'b2048encode',
     'b32ldecode', 'b32lencode', 'b64encode', 'b64decode', 'cb32encode',
-    'cb32decode', 'chalk', 'count_ones', 'dei_args', 'deprecated',
+    'cb32decode', 'chalk', 'cooldown', 'count_ones', 'dei_args', 'deprecated', 'do_not_flood',
     'future', 'ilex', 'join_bits', 'jsonencode', 'kwargs_prefix', 
     'lex', 'ltuple', 'makelist', 'mask_shift',
     'matches', 'mod_ceil', 'mod_floor', 'must_be', 'none_pass', 'not_implemented',
diff --git a/src/suou/functools.py b/src/suou/functools.py
index dafd0d6..d7d1166 100644
--- a/src/suou/functools.py
+++ b/src/suou/functools.py
@@ -382,6 +382,32 @@ def cooldown(unit: int, /, exception: Exception | None = None):
         return wrapper
     return decorator
 
+def do_not_flood(unit = .25):
+    """
+    Implement a calling cooldown for a function or procedure.
+
+    If the decorated function is called during the cooldown, the function
+    blocks before being called again.
+
+    This is blocking and uses time.sleep().
+    """
+    def decorator(func):
+        @wraps(func)
+        def wrapper(*args, **kwargs):
+            now = time.time()
+            if wrapper.timeout_until is not None and wrapper.timeout_until > now:
+                wrapper.timeout_delay += unit
+                time.sleep(wrapper.timeout_until - now)
+                wrapper.timeout_until = now + wrapper.timeout_delay
+            else:
+                wrapper.timeout_delay = unit
+                wrapper.timeout_until = time.time() + unit
+            return func(*args, **kwargs)
+        wrapper.timeout_until = None
+        wrapper.timeout_delay = unit
+        return wrapper
+    return decorator
+
 __all__ = (
-    'deprecated', 'not_implemented', 'timed_cache', 'none_pass', 'alru_cache', 'cooldown'
+    'deprecated', 'not_implemented', 'timed_cache', 'none_pass', 'alru_cache', 'cooldown', 'do_not_flood'
 )