FAQ about Managed Service for YDB

This page provides answers to common questions about Managed Service for YDB. For frequently asked questions about YDB, see this article.

Managed Service for YDB databases in serverless modeManaged Service for YDB databases in serverless mode

How do secondary and vector indexes impact the cost of a request?How do secondary and vector indexes impact the cost of a request?

Operations with indexes are billed according to the same rules as operations with tables. You can see them in the request statistics and they are included in the total values used to calculate the cost in request units (RUs). For more information, see the pricing policy for the YDB API serverless mode.

When reading data from a table using an index, the request statistics will show the number of records read from the index and their size.

Secondary indexesSecondary indexes

Adding a new row to a table creates a record in each existing secondary index. This will result in the change in both the number of added records and the size of written data in the statistics.

When you update a table row, the statistics will reflect the operations of deleting the old record and adding the new one for each secondary index that includes the updated fields.

When you delete a table row, the statistics will include the deletion of records from all secondary indexes of this table.

Vector indexesVector indexes

For a single-vector request to an index of the vector_kmeans_tree type, reading takes several stages:

1. Navigating the index tree.
   At each of the levels tree levels, KMeansTreeSearchTopSize clusters (each containing clusters subclusters) are selected from the existing clusters.
   Thus, the total number of required readings at this stage is around ${KMeansTreeSearchTopSize} * {levels} * {clusters}$.

2. Processing final candidates.
   At the lowest index tree level, all rows from the selected clusters get processed.
   The number of readings at this stage is around ${KMeansTreeSearchTopSize} * N / {clusters}^{levels}$ (in a balanced tree, where N is the total number of rows).
   If you do not use a covering index, a row will be additionally read from the main table for each candidate record found via the index.

What does the RESOURCE_EXHAUSTED error mean?What does the RESOURCE_EXHAUSTED error mean?

This error means a limit has been reached.

Check the throughput capacity in the YDB cluster settings and increase it, if needed. If the issue persists after you increase the throughput limit or the quota is exceeded, contact support.

What does the ThrottlingException error mean?What does the ThrottlingException error mean?

This error means that you have exceeded the quota for RUs (request units) consumption per second.

You can change quotas for an individual database in its settings (see Updating serverless database parameters). If you want to increase your cloud quota, contact support.

To prevent users from overconsuming RUs, we recommend setting the maximum consumption limit.