Update TiDB Serverless FAQ

Signed-off-by: Xiaoguang Sun <[email protected]>

tidb-cloud/serverless-faqs.md

@@ -20,29 +20,55 @@ TiDB Serverless offers the TiDB database with full HTAP capabilities for you and
 
 Get started with the 5-minute [TiDB Cloud Quick Start](/tidb-cloud/tidb-cloud-quickstart.md).
 
-### Is TiDB Serverless free during beta?
+### What are the limitations of a TiDB Serverless cluster?
 
-Until May 31, 2023, TiDB Serverless clusters are still free, with a 100% discount off. After that, usage beyond the free quota will be charged. Once the free quota of a cluster is reached, the read and write operations on this cluster will be throttled until you [increase the quota](/tidb-cloud/manage-serverless-spend-limit.md#update-spend-limit) or the usage is reset upon the start of a new month.
+For each organization in TiDB Cloud, you can create a maximum of five TiDB Serverless clusters by default. To create more TiDB Serverless clusters, you need to add a credit card and set a [spend limit](/tidb-cloud/tidb-cloud-glossary.md#spend-limit) for the usage.
+
+Some of TiDB Cloud features are partially supported or not supported on TiDB Serverless. See [TiDB Serverless Limitations and Quotas](/tidb-cloud/serverless-limitations.md) for details.
+
+### When will TiDB serverless be available on cloud platforms other than AWS, such as GCP or Azure?
+
+We are constantly working to bring TiDB serverless to other cloud platforms, including GCP and Azure. However, we can't give an exact timeline yet as we are still in the process of filling gaps and ensuring that the service works seamlessly in all environments. Rest assured that we are working hard to make TiDB serverless available on more cloud platforms, and we will keep our community updated once we have more information.
+
+### I created a Developer Tier cluster before TiDB Serverless was available. Can I still use my cluster?
+
+Yes, your Developer Tier cluster has been automatically migrated to the TiDB Serverless cluster, providing you with an improved user experience without any disruptions to your prior usage.
+
+## Billing and Metering FAQs
+
+### What are Request Units?
+
+TiDB Serverless adopts a pay-as-you-go model, which entails that you only pay for the storage space and usage of your cluster. In this model, all cluster activities such as SQL queries, bulk operations, and background jobs are quantified in [Request Units (RUs)](/tidb-cloud/tidb-cloud-glossary.md#request-unit). RUs offer an abstract measurement of the size and intricacy of requests initiated on your cluster. See [TiDB Serverless Pricing Details](https://www.pingcap.com/tidb-cloud-serverless-pricing-details/) for more information.
+
+### Is there any free plan available for TiDB Serverless?
+
+For the first five TiDB Serverless clusters in your organization, TiDB Cloud provides a free usage quota for each of them as follows:
+- Row storage: 5 GiB
+- [Request Units (RUs)](/tidb-cloud/tidb-cloud-glossary.md#request-unit): 50 million RUs per month
+
+Usage beyond the free quota will be charged. Once the free quota of a cluster is reached, the read and write operations on this cluster will be throttled until you [increase the quota](/tidb-cloud/manage-serverless-spend-limit.md#update-spend-limit) or the usage is reset upon the start of a new month.
 
 For more information, see [TiDB Serverless usage quota](/tidb-cloud/select-cluster-tier.md#usage-quota).
 
-### What does it mean for beta release?
+### How can I estimate the number of RUs required by my workloads and plan for monthly budget?
 
-TiDB Serverless is in beta while we continuously add new features and improve existing features before it becomes generally available. We do not provide SLA for beta products. Therefore, TiDB Serverless should **NOT** be used in production currently.
+To estimate the RU consumption of individual SQL statements, you can use the [EXPLAIN ANALYZE](/tidb-cloud/sql-statement-explain-analyze.md) SQL statement. You can see the RUs and storage your cluster has used in the Usage this month section of the Cluster Overview page. With past resource usage data and real-time resource usage graphs available on the Usage this month page, you can establish a reasonable spend limit for your cluster with the Edit Spend Limit feature. See [Manage Spend Limit for TiDB Serverless clusters](/tidb-cloud/manage-serverless-spend-limit.md) for more information.
 
-### What are the limitations of a TiDB Serverless cluster in beta?
+### How the storage is being metered for TiDB Serverless
 
-For each organization in TiDB Cloud, you can create a maximum of five TiDB Serverless clusters by default. To create more TiDB Serverless clusters, you need to add a credit card and set a [spend limit](/tidb-cloud/tidb-cloud-glossary.md#spend-limit) for the usage.
+The storage is metered based on the amount of data stored in the TiDB cluster, measured in GB-months. This calculation is based on the sum of the size of all the tables and indexes in the cluster, without including data compression or replicas for high availability, and is multiplied by the number of hours the data is stored in the month.
 
-Some of TiDB Cloud features are partially supported or not supported on TiDB Serverless. See [TiDB Serverless Limitations and Quotas](/tidb-cloud/serverless-limitations.md) for details.
+### Why does the storage used size remain unchanged after dropping a table or database immediately?
 
-### What can TiDB Serverless be used for?
+TiDB retains dropped tables and databases for a period of time to ensure that transactions that depend on these tables can continue to run smoothly. Moreover, the extended retention time enables TiDB to provide the [FLASHBACK TABLE](/tidb-cloud/sql-statement-flashback-table.md)/[FLASHBACK DATABASE](/tidb-cloud/sql-statement-flashback-database.md) feature, which allows you to recover dropped tables and databases in the event that they were mistakenly deleted.
 
-You can use your TiDB Serverless cluster for non-production workloads such as prototype applications, development environments, hackathons, and academic courses, or to provide temporary data service for your datasets.
+### Why are there RU consumptions when I'm not actively running any query?
 
-### I created a Developer Tier cluster before TiDB Serverless was available. Can I still use my cluster?
+RU consumptions can occur in various scenarios. One common scenario is during background queries, such as the synchronization of schema changes between TiDB instances. Another scenario is when certain web console features generate queries, like loading schemas. These processes utilize RUs even without explicit user triggers.
 
-Yes, your Developer Tier cluster has been automatically migrated to the TiDB Serverless cluster, providing you with an improved user experience without any disruptions to your prior usage.
+### Why there is spike in RU usage when my workload is steady?
+
+A spike in RU usage can occur due to necessary background jobs in TiDB. These jobs, such as automatically analyzing tables and rebuilding statistic data, are required for generating optimized query plans.
 
 ## Security FAQs