EDU-3861: HAN prototyping

docs/production-deployment/cloud/high-availability/enable.mdx

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+---
+id: enable
+title: Enable high availability
+sidebar_label: Enable high availability
+slug: /cloud/high-availability/choosing-high-availability
+description: Temporal Cloud's High-Availability Namespaces offer automated failover, synchronized data replication, and high availability for workloads requiring disaster-tolerant deployment and 99.99% uptime. Use Global Namespace for self-hosted.
+tags:
+  - Temporal Cloud
+  - Production
+  - High availability
+keywords:
+  - availability
+  - explanation
+  - failover
+  - high-availability
+  - multi-region
+  - multi-region namespace
+  - namespaces
+  - temporal-cloud
+  - term
+---
+import { RelatedReadContainer, RelatedReadItem } from '@site/src/components/related-read/RelatedRead';
+
+:::tip Support, stability, and dependency info
+
+High-availability Namespaces are in [Public Preview](/evaluate/development-production-features/release-stages#public-preview) for Temporal Cloud.
+
+:::
+
+You can enable the high-availability Namespace feature for your existing Namespace by [adding a second zone](#add-zones) to your Namespace.
+After adding the second zone, Temporal Cloud begins data replication for your new standby replica.
+Temporal Cloud notifies you once the replication has caught up and both Namespace zones are in sync.
+
+**Advantages of using a high-availability Namespace:**
+
+- No manual deployment or configuration needed, just simple push-button operation.
+- Open Workflows continue in the standby region with minimal interruption and data loss.
+- No changes needed for Worker and Workflow code during setup or failover.
+- 99.99% Contractual SLA.
+
+## Upgrade an existing single-zone Namespace for high-availability functionality {#add-zones}
+
+You can upgrade existing ssingle-zone Namespace for high-availability by adding a standby zone.
+The following sections show you how.
+
+<div style={{backgroundColor: '#ffff00',padding: '0px 15px',borderRadius: '5px',border: '1px solid #cccccc',display: 'inline-block'}}>**The following material has not been audited for MRN/HAN**</div>
+
+#### Temporal Cloud Web UI
+
+To upgrade an existing Namespace to a multi-region Namespace:
+
+1. Visit Temporal Cloud [Namespaces](https://cloud.temporal.io/namespaces) in your Web browser
+1. Navigate to the Namespace details page
+1. Select the “Add a region” button.
+1. Select the standby region you want to add to this Namespace
+
+You will see an estimated time for replication.
+This time is based on your selection and the size and scale of Workflows in your Namespace,
+An email alert is sent once your multi-region Namespace is ready for use.
+
+#### Temporal 'tcld' CLI
+
+At the command line, enter:
+
+```
+tcld namespace add-region \
+    --namespace <namespace_id>.<account_id> \
+    --region <region>
+```
+
+Specify the region code for the new region to add.
+Before pressing return, add your authentication credentials. For example, `--ca-certificate-file <path-to-pem-file>`.
+An email alert is sent once your multi-region Namespace is ready for use.
+
+### Discontinuing multi-region availability {#discontinuing}
+
+Disabling multi-region removes the high availability and automatic failover features that provide Temporal's highest service level agreement.
+To disable the feature and end charges, users must contact [Temporal Support](https://support.temporal.io) directly.
+MRN-specific charges for replication will stop once this decommissioning procedure completes.
+
+- When making your request you must let us know which region you want the Namespace to land in after removing the standby region.
+- If you cease services in the middle of the month, your Namespace will be converted to a single region Namespace within 1 business day.
+- Temporal won't retain replicated data in the standby region once multi-region has been disabled.
+- After disabling multi-region, Temporal Cloud cannot re-enable the feature for a given Namespace for seven days.

docs/production-deployment/cloud/high-availability/faq.mdx

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+---
+id: faq
+title: Frequently Asked Questions
+sidebar_label: Frequently Asked Questions
+slug: /cloud/high-availability/faq
+description: Temporal Cloud's High-Availability Namespaces offer automated failover, synchronized data replication, and high availability for workloads requiring disaster-tolerant deployment and 99.99% uptime. Use Global Namespace for self-hosted.
+tags:
+  - Temporal Cloud
+  - Production
+  - High availability
+keywords:
+  - availability
+  - explanation
+  - failover
+  - high-availability
+  - multi-region
+  - multi-region namespace
+  - namespaces
+  - temporal-cloud
+  - term
+---
+import { RelatedReadContainer, RelatedReadItem } from '@site/src/components/related-read/RelatedRead';
+
+:::tip Support, stability, and dependency info
+
+High-availability Namespaces are in [Public Preview](/evaluate/development-production-features/release-stages#public-preview) for Temporal Cloud.
+
+:::
+

docs/production-deployment/cloud/high-availability/how-it-works.mdx

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+---
+id: how-it-works
+title: How it works
+sidebar_label: How it works
+slug: /cloud/high-availability/how-it-works
+description: Temporal Cloud's High-Availability Namespaces offer automated failover, synchronized data replication, and high availability for workloads requiring disaster-tolerant deployment and 99.99% uptime. Use Global Namespace for self-hosted.
+tags:
+  - Temporal Cloud
+  - Production
+  - High availability
+keywords:
+  - availability
+  - explanation
+  - failover
+  - high-availability
+  - multi-region
+  - multi-region namespace
+  - namespaces
+  - temporal-cloud
+  - term
+---
+import { RelatedReadContainer, RelatedReadItem } from '@site/src/components/related-read/RelatedRead';
+
+:::tip Support, stability, and dependency info
+
+High-availability Namespaces are in [Public Preview](/evaluate/development-production-features/release-stages#public-preview) for Temporal Cloud.
+
+:::
+
+In traditional active/active replication, multiple nodes serve requests and accept writes simultaneously, ensuring strong synchronous data consistency.
+In contrast, with a Temporal Cloud high-availability Namespace, only the active zone accepts requests and writes at any given time.
+Workflow history events are written to the active zone first and then asynchronously replicated to the standby zone replica, ensuring that the replica remains in sync.
+
+<div style={{backgroundColor: '#ffff00',padding: '0px 15px',borderRadius: '5px',border: '1px solid #cccccc',display: 'inline-block'}}>**Needs new images**</div>
+
+|                      Before failover                      |                     After failover                      |
+| :-------------------------------------------------------: | :-----------------------------------------------------: |
+| ![Before failover](/img/multi-region/before-failover.png) | ![After failover](/img/multi-region/after-failover.png) |
+
+## Failovers {#failovers}
+
+A failover shifts Workflow Execution processing from an active Temporal Namespace region to a standby Temporal Namespace region during outages or other incidents.
+Standby Namespace regions use replication to duplicate data and prevent data loss during failover.
+
+**What happens during the failover process?**
+
+Temporal Cloud initiates a Namespace failover when it detects an incident or outage that raises error rates or latency in the active region of a multi-region Namespace.
+The failover shifts Workflow processing to a standby region that isn’t affected by the incident.
+This lets existing Workflows continue and new Workflows start while the incident is fixed.
+Once the incident is resolved, Temporal Cloud performs a "failback" by shifting Workflow Execution processing back to the original region.
+
+
+:::info
+
+You can test the failover of your multi-region Namespace by manually [triggering a failover](/cloud/multi-region#triggering-failovers) using the UI page or the 'tcld' CLI utility.
+In most scenarios, we recommend you let Temporal handle failovers for you.
+
+:::
+
+## Health Checks {#healthchecks}
+
+**How does Temporal detect failover conditions?**
+
+Temporal Cloud automates failovers by performing internal health checks.
+This process monitors your request error rates, latencies, and any infrastructure issues that might cause service disruptions, such as request timeouts.
+It automatically triggers failovers when these indicators exceed our allowed thresholds.
+
+### Replication lag {#replication-lag}
+
+Multi-region Namespaces use asynchronous replication between regions.
+Workflow updates in the active region, along with associated history events, are transmitted to the standby region with a short delay.
+This delay is called the replication lag.
+Temporal Cloud strives to maintain a P95 replication delay of less than 1 minute.
+In this context, P95 means 95% of requests are processed faster than this specified limit.
+
+Replication lags mean a [forced failover](/cloud/multi-region#forced-failover) may cause Workflows to rollback in progress.
+Lags may also cause recently started Workflows to be temporarily unavailable until the active region recovers.
+Temporal event versioning and [conflict resolution mechanisms](/cloud/multi-region#conflict-resolution) help guarantee that the Workflow Event History can be replayed.
+Critical operations like Signals won't get lost.
+
+### Failover scenarios
+
+The Temporal Cloud failover mechanism supports several modes to execute Namespace failovers.
+These modes include graceful failover ("handover"), forced failover, and a hybrid mode.
+The hybrid mode is Temporal Cloud’s default Namespace behavior.
+
+#### Graceful failover (handover) {#graceful-failover}
+
+In this mode, replication tasks are fully processed and drained.
+Temporal Cloud pauses traffic to the Namespace before the failover.
+This prevents the loss of progress and avoids data conflicts.
+The Namespace experiences a short period of unavailability, defaulting to 10 seconds.
+
+During this period, existing Workflows stop progress.
+Temporal Cloud returns a "Service unavailable error", which is retried by SDKs.
+State transitions will not happen and tasks are not dispatched.
+User requests like start/signal workflow will be rejected while operations are paused during handover.
+
+This mode favors _consistency_ over availability.
+
+#### Forced failover {#forced-failover}
+
+In this mode, a Namespace immediately activates in the standby region.
+Events not replicated due to [replication lag](/cloud/multi-region#replication-lag) will undergo [conflict resolution](/cloud/multi-region#conflict-resolution) upon reaching the new active region.
+
+This mode prioritizes _availability_ over consistency.
+
+#### Hybrid failover mode {#hybrid-failover}
+
+While graceful failovers are preferred for consistency, they aren’t always practical.
+Temporal Cloud’s hybrid failover mode (the default mode) limits an initial graceful failover attempt to 10 seconds or less.
+During this period, existing Workflows stop progress.
+Temporal Cloud returns a "Service unavailable error", which is retried by SDKs.
+If the graceful approach doesn’t resolve the issue, Temporal Cloud automatically switches to a forced failover.
+This strategy balances consistency and availability requirements.
+
+See the sections on [triggering a failover](/cloud/multi-region#triggering-failovers), [Worker deployment](/cloud/multi-region#worker-deployment), and [routing](/cloud/multi-region#routing) for more information.

docs/production-deployment/cloud/high-availability/index.mdx

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+---
+id: index
+title: High-availability Namespaces
+sidebar_label: High-availability Namespaces
+slug: /cloud/high-availability
+description: Temporal Cloud's High-Availability Namespaces offer automated failover, synchronized data replication, and high-availability for workloads requiring disaster-tolerant deployment and 99.99% uptime. Use Global Namespace for self-hosted.
+tags:
+  - Temporal Cloud
+  - Production
+  - High availability
+keywords:
+  - availability
+  - explanation
+  - failover
+  - high-availability
+  - multi-region
+  - multi-region namespace
+  - namespaces
+  - temporal-cloud
+  - term
+---
+
+import { RelatedReadContainer, RelatedReadItem } from '@site/src/components/related-read/RelatedRead';
+
+:::tip Support, stability, and dependency info
+
+High-availability Namespaces are in [Public Preview](/evaluate/development-production-features/release-stages#public-preview) for Temporal Cloud.
+
+:::
+
+Temporal Cloud's high-availability Namespaces provide disaster-tolerant deployment for workloads where availability is critical to your operations.
+When you enable high availability, Temporal Cloud automatically synchronizes your data between a primary and a fallback Namespace, keeping them in sync.
+Should an incident occur, Temporal will [failover](/glossary#failover) your Namespace.
+This allows your Workflow Executions and Schedules to seamlessly shift from the active availability zone to the fallback availability zone.
+
+## Availability zones and replicas
+
+An availability zone is a physically isolated data center within a deployment region for a given cloud provider.
+Regions consist of multiple availability zones, providing redundancy and fault tolerance.
+In some cases, the fallback zone may be in the same region as the primary zone, or it may be in a different region altogether, depending on your deployment configuration.
+
+High-availability simplifies deployment, ensuring operational continuity and data integrity even during unexpected events.
+Regional disruptions or other issues that affect the data centers within a specific availability zone may occur.
+High-availability allows processing to shift from the affected zone to an already-synchronized fallback zone.
+
+This synchronized zone is called a "replica."
+The process of duplicating all Workflow data ensures that your replica, which serves as the standby region, is always available and ready to take on the active role.
+
+In the event of network service or performance issues in the active zone, your replica is ready to take over.
+When necessary, Temporal Cloud smoothly transitions control from the active to the standby zone using a process called "[failover](/glossary#failover)".
+
+## Why choose high-availability? {#high-availability-intro}
+
+For many organizations, ensuring high-availability is critical to maintaining business continuity.
+Temporal Cloud's high-availability Namespace feature includes a 99.99% contractual Service Level Agreement ([SLA](https://docs.temporal.io/cloud/sla)).
+It provides 99.99% availability and 99.99% guarantee against service errors.
+
+A high-availability Namespace (HAN) creates a single logical Namespace that operates across two physical zones: one active and one standby.
+HANs streamline access for both zones to a unified Namespace endpoint.
+As Workflows progress in the active zone, history events are asynchronously replicated to the standby zone, ensuring continuity and data integrity.
+
+In the event of an incident or outage in the active zone, Temporal Cloud will seamlessly failover to your standby zone.
+Failovers allow existing Workflow Executions to continue running and new Workflow Executions to be started.
+Once failover occurs, the roles of the active and standby zones switch.
+The standby zone becomes active, and the previous active zone becomes the standby.
+After the issue is resolved, the zone "fails back" from the replica to the original.
+
+## Opting into high-availability
+
+Should you be using high-availability Namespaces? It depends on your availability requirements:
+
+- High-availability Namespaces offer a 99.99% contractual SLA for workloads with strict high-availability needs.
+  HANs use two Namespaces in two deployment zones to support standby recovery.
+  In the event of a zone failure, Temporal Cloud automatically fails over the HAN Namespace to the standby replica.
+- Single-zone Namespaces include a 99.9% contractual Service Level Agreement ([SLA](/cloud/sla)).
+  In single-zone use, Temporal clients connect to a single Namespace in one deployment zone.
+  For many applications, this offers sufficient availability.
+
+Temporal Cloud provides 99.99% service availability for all Namespaces, both single-region and high-availability.
+
+| **Advantages of using a multi-region Namespace**                                     |
+| ------------------------------------------------------------------------------------ |
+| No manual deployment or configuration required—just simple push-button operation.    |
+| Open Workflows continue in the standby zone with minimal interruption and data loss. |
+| No changes needed for Worker or Workflow code during setup or failover.              |
+| 99.99% contractual SLA.                                                              |
+

docs/production-deployment/cloud/high-availability/operations.mdx

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+---
+id: operations
+title: Operations
+sidebar_label: Operations
+slug: /cloud/high-availability/operations
+description: Temporal Cloud's High-Availability Namespaces offer automated failover, synchronized data replication, and high availability for workloads requiring disaster-tolerant deployment and 99.99% uptime. Use Global Namespace for self-hosted.
+tags:
+  - Temporal Cloud
+  - Production
+  - High availability
+keywords:
+  - availability
+  - explanation
+  - failover
+  - high-availability
+  - multi-region
+  - multi-region namespace
+  - namespaces
+  - temporal-cloud
+  - term
+---
+import { RelatedReadContainer, RelatedReadItem } from '@site/src/components/related-read/RelatedRead';
+
+:::tip Support, stability, and dependency info
+
+High-availability Namespaces are in [Public Preview](/evaluate/development-production-features/release-stages#public-preview) for Temporal Cloud.
+
+:::
+
+

docs/production-deployment/cloud/high-availability/pricing.mdx

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+---
+id: pricing
+title: Pricing (and Support?)
+sidebar_label: Pricing (and Support?)
+slug: /cloud/high-availability/pricing
+description: Temporal Cloud's High-Availability Namespaces offer automated failover, synchronized data replication, and high availability for workloads requiring disaster-tolerant deployment and 99.99% uptime. Use Global Namespace for self-hosted.
+tags:
+  - Temporal Cloud
+  - Production
+  - High availability
+keywords:
+  - availability
+  - explanation
+  - failover
+  - high-availability
+  - multi-region
+  - multi-region namespace
+  - namespaces
+  - temporal-cloud
+  - term
+---
+import { RelatedReadContainer, RelatedReadItem } from '@site/src/components/related-read/RelatedRead';
+
+:::tip Support, stability, and dependency info
+
+High-availability Namespaces are in [Public Preview](/evaluate/development-production-features/release-stages#public-preview) for Temporal Cloud.
+
+:::
+