> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kvant.sbs/jeston/llms.txt
> Use this file to discover all available pages before exploring further.

# React SSR and hydration

# React SSR and hydration

***

## Core · React SSR

> **Core principle** — Use server rendering to deliver useful HTML without turning hydration into an invisible second application.

A render path with explicit data ownership, hydration assumptions, and recovery behavior.

### Key concepts

<Columns cols={3}>
  <Card title="Server" icon="sparkles">
    HTML and initial data
  </Card>

  <Card title="Client" icon="shield-check">
    Events and local state
  </Card>

  <Card title="Failure" icon="gauge-high">
    Fallback and status
  </Card>
</Columns>

### Boundary model

```mermaid placement="top-right" theme={null}
sequenceDiagram
    participant Request
    participant Loader
    participant React
    participant Browser
    Request->>Loader: Resolve server data
    Loader->>React: Render with stable props
    React-->>Browser: HTML and serialized state
    Browser->>React: Hydrate interactive islands
```

### Ownership matrix

| Concern | Jeston/application boundary | Review signal                             |
| ------- | --------------------------- | ----------------------------------------- |
| Server  | HTML and initial data       | Optimize time to useful content.          |
| Client  | Events and local state      | Avoid duplicating server ownership.       |
| Failure | Fallback and status         | Do not render a misleading success shell. |

### Engineering considerations

SSR performance is determined by data dependencies, serialization, cache behavior, and client takeover—not only render speed.

> **Design constraint**
>
> SSR is a contract between two runtimes: server output and browser continuation.

### Implementation notes

| Engineering move            | Guidance                                                      |
| --------------------------- | ------------------------------------------------------------- |
| **Classify the data**       | Separate request-specific, cacheable, and client-only values. |
| **Render the useful shell** | Deliver meaningful structure before optional work.            |
| **Keep props serializable** | Avoid hidden runtime objects crossing the server boundary.    |
| **Test hydration failure**  | Check mismatches, slow data, and server error rendering.      |

### Decision lens

| Mode                 | Practical emphasis                            |
| -------------------- | --------------------------------------------- |
| **Fast page**        | Prefer bounded data and a small initial tree. |
| **Streaming page**   | Reveal independent sections progressively.    |
| **Interactive page** | Keep client state narrow and deliberate.      |

## Related topics

<Columns cols={3}>
  <Card title="Add streaming" icon="stream" horizontal href="/jeston/jeston/core/execution-and-streaming">
    Read the focused guide for this boundary.
  </Card>

  <Card title="Evaluate RSC" icon="atom" horizontal href="/jeston/jeston/core/react-server-components">
    Read the focused guide for this boundary.
  </Card>

  <Card title="Coordinate cache" icon="layer-group" horizontal href="/jeston/jeston/platform/cache-jobs-storage">
    Read the focused guide for this boundary.
  </Card>
</Columns>

<Columns cols={3}>
  * [stream · **Add streaming**](/jeston/jeston/core/execution-and-streaming) — Read the focused guide for this boundary.
  * [atom · **Evaluate RSC**](/jeston/jeston/core/react-server-components) — Read the focused guide for this boundary.
  * [layer-group · **Coordinate cache**](/jeston/jeston/platform/cache-jobs-storage) — Read the focused guide for this boundary.
</Columns>

## References

[1]: https://github.com/jeffersoncampos12p-dev/jeston "Jeston source repository"

[2]: https://www.npmjs.com/package/@kvantjs/jeston "Jeston package on npm"

[3]: https://nodejs.org/api/http.html "Node.js HTTP API"

[4]: https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal "AbortSignal Web API"

[5]: https://react.dev/reference/react-dom/server "React server rendering APIs"

[6]: https://www.typescriptlang.org/docs/handbook/intro.html "TypeScript handbook"