> ## Documentation Index
> Fetch the complete documentation index at: https://nexus-core.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Request Types in Nexus Core

> Nexus Core supports nine request types covering CRUD, atomic increments, leaderboard queries, broadcasting, and cache preloading over Redis pub/sub.

Every packet sent to Nexus Core includes a `type` field that identifies the operation to perform. Nexus Core supports nine request types, each with a defined MongoDB operation and cache behavior. Understanding these types helps you choose the right one for each use case and reason about performance and consistency trade-offs.

## All Request Types

| Type             | Description                                        | MongoDB Operation                | Cache Behavior |
| ---------------- | -------------------------------------------------- | -------------------------------- | -------------- |
| `GET_DATA`       | Retrieves a document by its ID field               | `findOne()`                      | Read-through   |
| `SET_DATA`       | Inserts or updates a document                      | `replaceOne(upsert)`             | Write-through  |
| `REMOVE_DATA`    | Deletes a document by its ID                       | `deleteOne()`                    | Invalidate     |
| `INCREMENT_DATA` | Atomically increments a numeric field              | `findOne()` + in-memory mutation | Write-through  |
| `UPDATE_DATA`    | Partially updates fields in an existing document   | `updateOne()`                    | Write-through  |
| `RANKING`        | Retrieves a global Top-N leaderboard (ASC or DESC) | Sorted query                     | Bypass         |
| `RANK_FINDER`    | Calculates a key's position in the global ranking  | Optimized query                  | Bypass         |
| `BROADCAST`      | Sends data to a target server via Redis pub/sub    | None                             | Bypass         |
| `LOAD_CACHE`     | Preloads a document into memory by ID              | `findOne()`                      | Warm           |

<Note>
  `RANKING` and `RANK_FINDER` bypass the cache entirely to guarantee a consistent global view of sorted data. `BROADCAST` has no MongoDB operation — it only routes a payload to another server's Redis channel.
</Note>

## Common Request Types in Detail

### GET\_DATA

Retrieves a single document by its `isId` field value. Nexus Core checks the Redis L2 cache first. On a cache miss, it queries MongoDB and writes the result back to both cache layers before returning.

Example `data` payload:

```json theme={null}
{
  "uuid": "550e8400-e29b-41d4-a716-446655440000"
}
```

### SET\_DATA

Inserts a new document or replaces an existing one using `replaceOne` with upsert. The updated document is written through to both Redis and the L1 in-memory cache.

Example `data` payload:

```json theme={null}
{
  "uuid": "550e8400-e29b-41d4-a716-446655440000",
  "kills": 142,
  "deaths": 38,
  "balance": 2500.75,
  "isPremium": true
}
```

### REMOVE\_DATA

Deletes a document by its ID and invalidates the corresponding Redis and L1 cache entries.

Example `data` payload:

```json theme={null}
{
  "uuid": "550e8400-e29b-41d4-a716-446655440000"
}
```

### INCREMENT\_DATA

Atomically increments a numeric field (`int`, `long`, or `double`) without requiring a full `SET_DATA` round trip. Nexus Core reads the document, applies the mutation in memory, and writes the result back through the cache.

Example `data` payload:

```json theme={null}
{
  "uuid": "550e8400-e29b-41d4-a716-446655440000",
  "kills": 1
}
```

## Related Topics

* [Request Lifecycle](/reference/request-lifecycle) — how each type flows through validation, routing, and cache
* [Packet Structure](/reference/packet-structure) — the full JSON format for incoming and outgoing packets
* [Cache Strategy](/concepts/cache-strategy) — read-through, write-through, and invalidation behaviors


## Related topics

- [Request Lifecycle in Nexus Core](/reference/request-lifecycle.md)
- [Nexus Core Changelog](/reference/changelog.md)
- [Cache Strategy and Hierarchy in Nexus Core](/concepts/cache-strategy.md)
- [System Architecture of Nexus Core](/concepts/architecture.md)
- [DataAddon API Reference](/addons/data-addon-api.md)