## Bug description

Currently, decide endpoint takes 10+ seconds on kea.js.org.

This means that for first-time visitors autocapture nor session recording will be turned on for that long - losing valuable information.

When measuring this yesterday via shell ([slack thread](https://posthog.slack.com/archives/C0113360FFV/p1604951621008400)), the culprit was feature flags cohort checking. In this case, the cohort user was checked against was defined against the following action:

![Screenshot from 2020-11-10 11-41-32](https://user-images.githubusercontent.com/148820/98657215-49582e80-234a-11eb-9669-37d55e0d23bd.png)

Which currently looks through events of the data for that team.

## Expected behavior

Decide endpoint should use cached/materialized cohort ownership rather than calculating it on the fly.

## How to reproduce

1. Create an action with some selector
2. Create a cohort for has done action at any point
3. Create a feature flag using the cohort.
4. Measure /decide endpoint latency

## Environment

Cloud 

## Additional context

cc @EDsCODE who made it not time out by https://github.com/PostHog/posthog/pull/2299

#### *Thank you* for your bug report – we love squashing them!
posthog/celery.py
import os
import time
import statsd
from celery import Celery
from celery.schedules import crontab
from django.conf import settings
from django.db import connection
from django.utils import timezone
from posthog.ee import check_ee_enabled
from posthog.redis import get_client
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "posthog.settings")
app = Celery("posthog")
app.config_from_object("django.conf:settings", namespace="CELERY")
app.autodiscover_tasks()
app.conf.broker_pool_limit = 0
ACTION_EVENT_MAPPING_INTERVAL_MINUTES = 10
statsd.Connection.set_defaults(host=settings.STATSD_HOST, port=settings.STATSD_PORT)
@app.on_after_configure.connect
def setup_periodic_tasks(sender, **kwargs):