# HNSW Indexes and Custom Prompts!

By Daniel Chalef · Oct 04, 2023 · https://www.getzep.com/blog/hnsw-indexes-custom-prompts-and-more/ · Tags: Engineering, Product updates

Zep v0.13.0, released today, now includes support for HNSW indexes and the ability to set custom prompts for summarization tasks.

Zep v0.13.0, [released today](https://github.com/getzep/zep/releases/tag/v0.13.0), now includes support for `HNSW` indexes and the ability to set custom prompts for summarization tasks.

Hierarchical Navigable Small World (`HNSW`) indexes are faster and more accurate than `IVFFLAT` indexes previously used by Zep. Not only that, they are also simpler to maintain as they don't need a [manual "indexing" (or training) step](https://docs.getzep.com/sdk/documents/#indexing-a-collection).

## HNSW indexes

For new installs of Zep, Message vector search and [document Collections use HNSW indexes](https://docs.getzep.com/sdk/documents/#indexes) by default.

For upgrades, only *new* document Collections will be indexed with HNSW.

To determine the index type of a Collection, view the Collection's details in the Zep web interface or query the [Zep API](https://docs.getzep.com/sdk/).

![Zep web interface Indexing panel for a collection showing status Indexed, type HNSW, and a disabled Force Index Collection button.](https://www.getzep.com/blog/hnsw-indexes-custom-prompts-and-more/image.png)

HNSW-indexed Collection

Query the Zep API for [collection details](https://docs.getzep.com/sdk/documents/#loading-an-existing-collection) (also available [via the TypeScript SDK)](https://docs.getzep.com/sdk/documents/#loading-an-existing-collection):

```python
collection = client.document.get_collection(collection_name)
```

### Prerequisites to using HNSW indexes

To use HNSW indexes. you must ensure that the Postgres database back-end you use offers `pgvector` v0.5 or later. This is the case when installing using Zep's `docker compose` install, but cloud providers may only offer earlier versions of `pgvector`.

The Zep logs will display a message similar to the following when HNSW indexes are available:

```text
INFO[2023-10-04T13:40:37-07:00] vector extension version is >= 0.5.0. hnsw indexing available
```

### Custom prompts

Custom [Summary Extractor prompts](https://docs.getzep.com/deployment/prompts/) are now available! You can configure these in Zeps `config.yaml` file or your environment.

```text
    # OpenAI summarizer prompt configuration.
    # Guidelines:
    # - Include {{.PrevSummary}} and {{.MessagesJoined}} as template variables.
    # - Provide a clear example within the prompt.
    #
    # Example format:
    # openai: |
    #   <YOUR INSTRUCTIONS HERE>
    #   Example:
    #     <PROVIDE AN EXAMPLE>
    #   Current summary: {{.PrevSummary}}
    #   New lines of conversation: {{.MessagesJoined}}
    #   New summary:`
    #
    # If left empty, the default OpenAI summary prompt from zep/pkg/extractors/prompts.go will be used.
    openai: |
```

Custom prompts can be configured to provide summaries in the language of your users or to improve the existing prompts for your particular business.

When used alongside a [local or open source LLM](https://docs.getzep.com/deployment/llm_config/#custom-openai-compatible-api-endpoint) with an OpenAI compatible API, custom prompts can be used to enable summarization for models that operate dissimilar to OpenAI's GPT-family or Anthropic's Claude models.

Thanks to [Brice Macias](https://github.com/bricemacias) for contributing this feature!

To learn more, read the [Custom Summary Extractor Prompts](https://docs.getzep.com/deployment/prompts/) documentation.