---
layout: docs
page_title: API list pagination
description: >-
  Learn about API pagination and how the cache works in Boundary to prevent system resources from being overwhelmed and to help you find resources.
---

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# API list pagination

Boundary uses an API pagination feature to support searching and filtering large lists of results without overwhelming your system resources.

## Introduction

When you perform a `list` operation on a resource, the API request returns the first 1000 results, by default.
You can request the next page of results by repeating the `list` command and including a parameter with a token provided by Boundary.

## Initial pagination

When you run a `list` operation on a resource, the initial results are sorted in descending order by creation time and public ID (most recently created first).
Boundary returns the maximum number of responses along with the top-level fields `response_type` and `list_token`.
If the `response_type` is `delta`, it means there are more items available in the list.

List tokens contain general metadata associated with the ongoing pagination.
To request the next page of results, run the `list` operation again and include the `list_token` that Boundary provided in the last response.
Boundary returns the next page of results with new `response_type` and `list_token` values.

![API pagination workflow](/img/api-pagination/pagination-workflow.png)

You can continue viewing new pages of results using the `list_token` values until the `response_type` reads `complete`.
If you compose an invalid token, you receive an invalid token error.

## Request updated and deleted resources

When the `response_type` reads `complete`, you have viewed all the results that were available when you ran the initial `list` operation.
You can now request any resources that were updated or deleted since you started paginating.

To refresh the cached list results, make another `list` request using the `list_token` from the previous response.
Boundary returns a `response_type` and `list_token` as part of the response, similarly to when you ran the initial operation.
If the `response_type` is `delta`, it means there are more items available in the list.
You can use the `list_token` as a parameter to continue viewing new pages of results until the `response_type` reads `complete`.

Boundary also includes the top-level response `removed_ids` as part of the refresh operation.
The `removed_ids` response contains the IDs of any resources that were deleted since you began paginating the results of the previous `list` operation.
Any resources that have been deleted are included on the first page of results.

After 30 days, the `list_token` expires and you must make a new `list` request without the token to regenerate the full list of results.
If you make a `list` request using a token that has a `create_time` older than 30 days, Boundary treats it as an invalid token and returns an error.

## Response structure

All `list` endpoints support the following parameters:

- `list_token` (optional) - An opaque token that is returned from the previous `list` response.
If you do not supply a value, pagination starts from the beginning.
- `page_size` (optional) - An unsigned integer that indicates the number of items that should be included on the page of search results.
If you do not include a value, or if you include a value of `0`, Boundary uses the default page size of 1000 items.
If you configure it, the `page_size` value overrides the default page size.
Controller administrators can also configure a `max_page_size` option that constrains the maximum page size a user can request.

Boundary returns the following response parameters:

- `response_type` - Defines whether the response is a `delta` or `complete` listing.
The value is `delta` until the last page is returned, at which point it will be `complete`.
- `list_token` - An opaque token which is included in subsequent listing requests after the initial one, so that the client can continue to paginate the results.
- `sort_by` - The column name that the returned items should be sorted on.
This attribute is included in the response, so that the sort order for each endpoint is explicit.
- `sort_dir` - The direction in which the returned items are sorted.
Responses can include `desc` for descending, or `asc` for ascending.
- `items` - The list of items.
- `est_item_count` - An unsigned integer that indicates the total number of items that are available in the list of results.
This number may be an estimate, since the number of items may change during the pagination process.

### Example response

```json
{
  "response_type": "<delta|complete>",
  "list_token": "<opaque-token>",
  "sort_by": "created_time",
  "sort_dir": "desc",
  "est_item_count": 1000,
  "items": [
    {
      "id": "ttcp_1234567890",
      "scope_id": "p_1234567890"
    },
    {
      "id": "ttcp_2234567890",
      "scope_id": "p_1234567890"
    }
  ]
}
```

## Constraints and limitations

In scenarios where updates are so frequent that the results may change while the refresh operation runs, those updates may not appear at all in the refreshed list.
If you make frequent updates to a resource, or if you are updating data while you run a `list` operation, HashiCorp recommends that you generate the full list of results instead of performing a refresh.

Workers are not included in refresh operations because the updates they send to the controller are too frequent to be captured in a refresh.
To update a list of worker resources, you must regenerate the full list of results.

When you refresh the list of results, you may notice duplicate items in the list.
This is a fundamental tradeoff when you search across multiple database transactions.