---
title: "server-zd reference"
description: "server-zd is a Dex Server whose only runtime dependency is object storage, such"
canonical_url: "https://docs.superdurable.io/zh-Hans/reference/server/"
source: "docs/reference/server/index.mdx"
locale: "zh-Hans"
---

# server-zd reference

server-zd is a Dex Server whose only runtime dependency is object storage, such
as Amazon S3 or an S3-compatible store. It keeps Flow state in a local store and
commits every write to object storage before it acknowledges the write. The
local disk is only a cache. A node rebuilds it from the latest snapshot and the
command log in object storage.

server-zd serves the **FlowService**, **WorkerTaskService**, and **AdminService** API. It supports
only [pull Workers](https://docs.superdurable.io/zh-Hans/reference/server/workers.md). Run [Dex Web](https://docs.superdurable.io/zh-Hans/reference/web/dex-web.md)
as a separate process; server-zd does not serve it. For local development, run
**dexcli dev**, which starts server-zd and Dex Web. To run one production node
on local disk without external object storage, see
[Single node on local disk](https://docs.superdurable.io/zh-Hans/reference/server/configuration.md#single-node-local). This reference covers server-zd
0.1. See [Server](https://docs.superdurable.io/zh-Hans/primitives/components/server.md) for how server-zd fits with the
other components.

## Pages

- [Flow and Step runtime](https://docs.superdurable.io/zh-Hans/reference/server/runtime-steps.md): start options,
  Flow configuration, waits, Step decisions, Step options, and failure and
  redelivery.
- [Data primitive semantics](https://docs.superdurable.io/zh-Hans/reference/server/runtime-data.md): detailed rules
  for Attributes, RPCs, Channels, Streams, and SubFlows, such as indexes,
  hard-delete Attributes, locks, transactional RPCs, and Stream limits.
- [Client requests](https://docs.superdurable.io/zh-Hans/reference/server/runtime-client.md): how the server handles
  each Client request, including Attribute reads, waits, and their limits.
- [Install and configure](https://docs.superdurable.io/zh-Hans/reference/server/configuration.md): install, minimal
  production configuration, a single node on local disk, retention, history window, limits, performance
  tuning, and Streams.
- [Kubernetes deployment](https://docs.superdurable.io/zh-Hans/reference/server/kubernetes.md): the StatefulSet,
  graceful shutdown, the local store volume, and health checks.
- [High availability](https://docs.superdurable.io/zh-Hans/reference/server/high-availability.md): the lease, hot
  standby, and step down.
- [Object storage and backup](https://docs.superdurable.io/zh-Hans/reference/server/object-storage.md): credentials,
  IAM policy, encryption, versioning, and restore.
- [Authentication](https://docs.superdurable.io/zh-Hans/reference/server/authentication.md): API and admin
  credentials.
- [Workers and task queue](https://docs.superdurable.io/zh-Hans/reference/server/workers.md): the Worker protocol,
  routing, capacity, shutdown, dispatch settings, and the Step task queue.
- [Search backends](https://docs.superdurable.io/zh-Hans/reference/server/search.md): the external search projection
  and PostgreSQL search.
- [Attribute Store sync](https://docs.superdurable.io/zh-Hans/reference/server/attribute-store-sync.md): behavior,
  configuration, fencing, retries, and table contracts.
- [Metrics and alerts](https://docs.superdurable.io/zh-Hans/reference/server/metrics.md): the Prometheus endpoint and
  alert rules.
- [Upgrades and compatibility](https://docs.superdurable.io/zh-Hans/reference/server/upgrades.md): protocol versions,
  upgrade order, and rollback.

## Unsupported features

server-zd rejects these options with **INVALID_ARGUMENT**:

- A Flow start delay, which is **flow_start_delay_seconds** greater than zero.
  Tracked in [issue 995](https://github.com/superdurable/dex/issues/995).
- A Flow-level retry policy, which is **retry_policy** in the Flow start
  options. Tracked in [issue 996](https://github.com/superdurable/dex/issues/996).
  Step-level retry is supported.

The only Attribute Store is PostgreSQL. Redis is tracked in
[issue 616](https://github.com/superdurable/dex/issues/616).

## Release notes

Each server-zd release lists its breaking changes, features, fixes, and upgrade
steps. See the
[server-zd releases](https://github.com/superdurable/dex/releases?q=server-zd\&expanded=true)
on GitHub.