---
title: live_at() | Tiger Data Docs
description: Test if the aggregate has a heartbeat covering a given time
---

Since [1.15.0](https://github.com/timescale/timescaledb-toolkit/releases/tag/1.15.0)

Determine whether the aggregate has a heartbeat indicating the system was live at a given time.

Note that this returns false for any time not covered by the aggregate.

## Samples

Given a table called `liveness` containing weekly heartbeat aggregates in column `health` with timestamp column `date`, use the following to see if the system was live at a particular time.

```
SELECT live_at(health, '2022-01-12 15:30:00+00')
FROM liveness
WHERE date = '01-9-2022 UTC'
```

Returns:

```
 live_at
---------
 f
```

## Arguments

The syntax is:

```
live_at(
    agg HEARTBEATAGG,
    test TIMESTAMPTZ
) RETURNS BOOL
```

| Name | Type         | Default | Required | Description                                         |
| ---- | ------------ | ------- | -------- | --------------------------------------------------- |
| agg  | HeartbeatAgg | -       | ✔        | A heartbeat aggregate to get the liveness data from |
| test | TimestampTz  | -       | ✔        | The time to test the liveness of                    |

## Returns

| Column   | Type | Description                                                                 |
| -------- | ---- | --------------------------------------------------------------------------- |
| live\_at | bool | True if the heartbeat aggregate had a heartbeat close before the test time. |