Update changelog.md - Adding more context on tiers & features

Author: tbragin

docs/en/cloud/reference/changelog.md

@@ -8,35 +8,55 @@ In addition to this ClickHouse Cloud changelog, please see the [Cloud Compatibil
 
 ## January 23, 2024
 
-### New pricing plans
+### Changes to ClickHouse Cloud tiers
 
-Launch of the new pricing plans. See our [launch blog](https://clickhouse.com/blog/evolution-of-clickhouse-cloud-new-features-superior-performance-tailored-offerings) for more information. The [FAQ](https://clickhouse.com/docs/en/cloud/manage/jan-2025-faq/summary) covers the key changes and dates. If you have any questions, please contact us at: `[email protected]`.
+We are dedicated to adapting our products to meet the ever-changing requirements of our customers. Since its introduction in GA over the past two years, ClickHouse Cloud has evolved substantially, and we've gained invaluable insights into how our customers leverage our cloud offerings. 
 
-### Compute-compute separation (GA)
+We are introducing new features to optimize the sizing and cost-efficiency of ClickHouse Cloud services for your workloads. These include **compute-compute separation**, high-performance machine types, and **single-replica services**. We are also evolving automatic scaling and managed upgrades to execute in a more seamless and reactive fashion. 
 
-Compute-compute separation is Generally Available; please refer to [blog](https://clickhouse.com/blog/introducing-warehouses-compute-compute-separation-in-clickhouse-cloud) for more details and the [documentation](https://clickhouse.com/docs/en/cloud/reference/warehouses).
+We are adding a **new Enterprise tier** to serve the needs of the most demanding customers and workloads, with focus on industry-specific security and compliance features, even more controls over underlying hardware and upgrades, and advanced disaster recovery features. 
 
-### HIPAA support
+To support these changes, we are restructuring our current **Development** and **Production** tiers to more closely match how our evolving customer base is using our offerings. We are introducing the **Basic** tier, oriented toward users that are testing out new ideas and projects, and the **Scale** tier, matching users working with production workloads and data at scale.
 
-We now support HIPAA in compliant regions, including AWS `us-east-1`, `us-west-2` and GCP `us-central1`, `us-east1`. Customers wishing to onboard must sign a Business Associate Agreement (BAA) and deploy to the compliant version of the region. For more information on HIPAA, please refer to the [documentation](https://clickhouse.com/docs/en/cloud/security/security-and-compliance).
+You can read about these and other functional changes in this [blog](https://clickhouse.com/blog/evolution-of-clickhouse-cloud-new-features-superior-performance-tailored-offerings). Existing customers will need to take action to select a [new plan](https://clickhouse.com/pricing). Customer-facing communication was sent via email to organization administrators, and the following [FAQ](https://clickhouse.com/docs/en/cloud/manage/jan-2025-faq/summary) covers the key changes and timelines. 
 
-### Configurable backups
+### Warehouses: Compute-compute separation (GA)
 
-We now support the ability for customers to export backups to their own cloud account; please refer to the [documentation](https://clickhouse.com/docs/en/cloud/manage/backups#configurable-backups) for additional information. 
+Compute-compute separation (also known as "Warehouses") is Generally Available; please refer to [blog](https://clickhouse.com/blog/introducing-warehouses-compute-compute-separation-in-clickhouse-cloud) for more details and the [documentation](https://clickhouse.com/docs/en/cloud/reference/warehouses).
+
+### Single-replica services
+
+We are introducing the concept of a “single-replica service”, both as a standalone offering and within warehouses. As a standalone offering, single-replica services are size limited and intended to be used for small test workloads. Within warehouses, single-replica services can be deployed at larger sizes, and utilized for workloads not requiring high availability at scale, such as restartable ETL jobs. 
+
+### Vertical auto-scaling improvements
+
+We are introducing a new autoscaling mechanism for vertical scaling of compute replicas, a concept we call “make before break” (or MBB). With this new approach, we add replica(s) of a new size before removing the old one(s) during the scaling operation. This results in more seamless scaling operations that are less disruptive to running workloads, because no capacity is lost during scaling. It is especially important during scale-up events as it is triggered by high resource utilization and removing replicas will make it worse. 
 
 ### Horizontal scaling (GA)
 
 Horizontal scaling is now Generally Available. Users can add additional replicas to scale out their service through the APIs and the cloud console. Please refer to the [documentation](https://clickhouse.com/docs/en/manage/scaling#self-serve-horizontal-scaling) for information.
 
+### Configurable backups
+
+We now support the ability for customers to export backups to their own cloud account; please refer to the [documentation](https://clickhouse.com/docs/en/cloud/manage/backups#configurable-backups) for additional information. 
+
+### Managed upgrade improvements
+
+Safe managed upgrades deliver significant value to our users by allowing them to stay current with the database as it moves forward to add features. With this rollout, we applied the “make before break” (or MBB) approach to upgrades, further reducing impact to running workloads. 
+
+### HIPAA support
+
+We now support HIPAA in compliant regions, including AWS `us-east-1`, `us-west-2` and GCP `us-central1`, `us-east1`. Customers wishing to onboard must sign a Business Associate Agreement (BAA) and deploy to the compliant version of the region. For more information on HIPAA, please refer to the [documentation](https://clickhouse.com/docs/en/cloud/security/security-and-compliance).
+
 ### Scheduled upgrades
 
 Users can schedule upgrades for their services. This feature is supported for Enterprise tier services only. For more information on Scheduled upgrades, please refer to the [documentation](https://clickhouse.com/docs/en/manage/updates).
 
-### Client support for complex types
+### Language client support for complex types
 
 [Golang](https://github.com/ClickHouse/clickhouse-go/releases/tag/v2.30.1), [Python](https://github.com/ClickHouse/clickhouse-connect/releases/tag/v0.8.11), and [NodeJS](https://github.com/ClickHouse/clickhouse-js/releases/tag/1.10.1) clients added support for Dynamic, Variant, and JSON types.
 
-### DBT supports Refreshable Materialized Views
+### DBT support for Refreshable Materialized Views
 
 DBT now [supports Refreshable Materialized Views](https://github.com/ClickHouse/dbt-clickhouse/releases/tag/v1.8.7) in the `1.8.7` release.
 
@@ -46,7 +66,7 @@ Support has been added for JWT-based authentication in the JDBC driver v2, click
 
 JDBC / Java will be in[ 0.8.0](https://github.com/ClickHouse/clickhouse-java/releases/tag/v0.8.0) when it's released - ETA pending.
 
-### Prometheus integration
+### Prometheus integration improvements
 
 We've added several enhancements for the Promethous integration: