## 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
from posthog.tasks.session_recording_retention import session_recording_retention_scheduler
    session_recording_retention_scheduler()
@app.task(ignore_result=True)
def calculate_event_action_mappings():
    from posthog.tasks.calculate_action import calculate_actions_from_last_calculation
    calculate_actions_from_last_calculation()
@app.task(ignore_result=True)
def calculate_cohort():
    from posthog.tasks.calculate_cohort import calculate_cohorts
    calculate_cohorts()
@app.task(ignore_result=True)
def check_cached_items():
    from posthog.tasks.update_cache import update_cached_items
    update_cached_items()
@app.task(ignore_result=True)
def update_cache_item_task(key: str, cache_type: str, payload: dict) -> None:
    from posthog.tasks.update_cache import update_cache_item
    update_cache_item(key, cache_type, payload)
@app.task(ignore_result=True)
def send_weekly_email_report():
    if settings.EMAIL_REPORTS_ENABLED:
        from posthog.tasks.email import send_weekly_email_reports
        send_weekly_email_reports()
@app.task(ignore_result=True, bind=True)
def debug_task(self):
    print("Request: {0!r}".format(self.request))