## 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!
ee/clickhouse/sql/person.py
).format(
    table_name=PERSONS_TABLE,
    engine=table_engine(PERSONS_TABLE, "_timestamp"),
    extra_fields=KAFKA_COLUMNS,
    storage_policy=STORAGE_POLICY,
)
KAFKA_PERSONS_TABLE_SQL = PERSONS_TABLE_BASE_SQL.format(
    table_name="kafka_" + PERSONS_TABLE, engine=kafka_engine(KAFKA_PERSON), extra_fields="",
)
PERSONS_TABLE_MV_SQL = """
CREATE MATERIALIZED VIEW {table_name}_mv 
TO {table_name} 
AS SELECT
id,
created_at,
team_id,
properties,
is_identified,
_timestamp,
_offset
FROM kafka_{table_name} 
""".format(
    table_name=PERSONS_TABLE
)
GET_LATEST_PERSON_SQL = """
SELECT * FROM person JOIN (
    SELECT id, max(created_at) as created_at FROM person WHERE team_id = %(team_id)s GROUP BY id
) as person_max ON person.id = person_max.id AND person.created_at = person_max.created_at
WHERE team_id = %(team_id)s
{query}