# PCACHE.CREATE

> Create a prompt cache namespace with an optional entry limit, default TTL and per-hit cost.

URL: https://docs.hotkv.com/commands/pcache-create/

```
PCACHE.CREATE namespace [MAX_ENTRIES n] [TTL seconds] [COST_PER_HIT usd]
```

- Group: Prompt cache
- Complexity: O(1)
- HotKV Cloud: Performance and Scale plans
- On-Premise: requires the prompt-cache license feature

The prompt cache is an exact-match cache for LLM prompt and response pairs, organised in named namespaces. `PCACHE.CREATE` creates a namespace. You must create a namespace
before you can store entries in it with [PCACHE.SET](https://docs.hotkv.com/commands/pcache-set/index.md).

## Options

| Option | Effect |
| --- | --- |
| `MAX_ENTRIES n` | Maximum number of entries. `0` or omitted uses the server's per-namespace limit, and larger values are capped at that limit (`max_entries_per_namespace` under `[pcache]`). When the namespace is full, HotKV evicts existing entries to make room, expired entries first. |
| `TTL seconds` | Default time to live for entries stored without their own `TTL`. `0` or omitted means entries do not expire. |
| `COST_PER_HIT usd` | A fixed dollar amount credited to `cost_saved_usd` in [PCACHE.STATS](https://docs.hotkv.com/commands/pcache-stats/index.md) for every hit. Must be zero or positive. Default `0`. |

Options can be given in any order and are case-insensitive. You can change
all three later with [PCACHE.CONFIG](https://docs.hotkv.com/commands/pcache-config/index.md).

## Return value

| Case | RESP2 | RESP3 |
| --- | --- | --- |
| Namespace created | Simple string `OK` | Same |

Errors:

- `ERR namespace already exists or limit reached` if the namespace exists, or the server already holds its maximum number of prompt cache namespaces (`max_namespaces` under `[pcache]`).
- `ERR invalid MAX_ENTRIES`, `ERR invalid TTL` or `ERR invalid COST_PER_HIT` if a value cannot be parsed or is negative.
- `ERR unknown option` for any other option name.
- `ERR wrong number of arguments for 'pcache.create' command` if the argument count is wrong.
- `NOLICENSE prompt-cache requires a HotKV license. Contact sales@hotkv.com` if your license does not include the `prompt-cache` feature.

## Examples

```
127.0.0.1:6379> PCACHE.CREATE llm_prompts MAX_ENTRIES 100000 TTL 3600 COST_PER_HIT 0.012
OK
127.0.0.1:6379> PCACHE.CREATE llm_prompts
(error) ERR namespace already exists or limit reached
```

## Compatibility

HotKV-only command. Redis and Valkey have no equivalent.

## See also

[PCACHE.SET](https://docs.hotkv.com/commands/pcache-set/index.md), [PCACHE.GET](https://docs.hotkv.com/commands/pcache-get/index.md), [PCACHE.GETEX](https://docs.hotkv.com/commands/pcache-getex/index.md), [PCACHE.DEL](https://docs.hotkv.com/commands/pcache-del/index.md), [PCACHE.STATS](https://docs.hotkv.com/commands/pcache-stats/index.md), [PCACHE.FLUSH](https://docs.hotkv.com/commands/pcache-flush/index.md), [PCACHE.DROP](https://docs.hotkv.com/commands/pcache-drop/index.md), [PCACHE.LIST](https://docs.hotkv.com/commands/pcache-list/index.md), [PCACHE.CONFIG](https://docs.hotkv.com/commands/pcache-config/index.md), [AI features guide](https://docs.hotkv.com/ai-features/index.md)