# Knowledge Base **URL:** https://forum.scylladb.com/c/knowledge-base/8.md [Latest](https://forum.scylladb.com/latest.md) · [Categories](https://forum.scylladb.com/categories.md) · [Tags](https://forum.scylladb.com/tags.md) --- ## [About the Knowledge Base category](https://forum.scylladb.com/t/about-the-knowledge-base-category/40)
**Author:** [@Guy](https://forum.scylladb.com/u/Guy)\ **Replies:** 0
Topics for understanding and troubleshooting ScyllaDB. These are frequently asked questions and general topics. --- ## [Scylla manager task healthcheck/cql frequency update](https://forum.scylladb.com/t/scylla-manager-task-healthcheck-cql-frequency-update/814)
**Author:** [@jchinmay219](https://forum.scylladb.com/u/jchinmay219)\ **Replies:** 1\ **Last updated:** [September 11, 2023, 7:13am UTC](https://forum.scylladb.com/t/scylla-manager-task-healthcheck-cql-frequency-update/814 "2023-09-11T07:13:23Z")
Can I update the frequency of default scylla manager task healthcheck/cql with sctool commands. --- ## [Maximizing read throughput of table scan using shard-awareness](https://forum.scylladb.com/t/maximizing-read-throughput-of-table-scan-using-shard-awareness/764)
**Author:** [@rado](https://forum.scylladb.com/u/rado)\ **Replies:** 1\ **Last updated:** [August 8, 2023, 2:03pm UTC](https://forum.scylladb.com/t/maximizing-read-throughput-of-table-scan-using-shard-awareness/764 "2023-08-08T14:03:33Z")
I would love any feedback on this blog that I just posted. Is the general idea correct? Am I missing anything important? Am I actually misleading anyone? Thanks https://buransky.com/programming/maximizing-read-throughpu… --- ## [Scylla DB use case to replace very slow RDBMS Common Table Expression](https://forum.scylladb.com/t/scylla-db-use-case-to-replace-very-slow-rdbms-common-table-expression/647)
**Author:** [@Sam](https://forum.scylladb.com/u/Sam)\ **Replies:** 6\ **Last updated:** [July 14, 2023, 5:19pm UTC](https://forum.scylladb.com/t/scylla-db-use-case-to-replace-very-slow-rdbms-common-table-expression/647 "2023-07-14T17:19:15Z")
I currently employ a relational database CTE that iterates over parentage information to find all ancestors or all descendants of a given entity. Even on a small (150000) sample, it can take over an hour to return a resu… --- ## [How Does ScyllaDB Find the Node Containing the Data I Want?](https://forum.scylladb.com/t/how-does-scylladb-find-the-node-containing-the-data-i-want/161)
**Author:** [@Guy](https://forum.scylladb.com/u/Guy)\ **Replies:** 0\ **Last updated:** [December 11, 2022, 7:53am UTC](https://forum.scylladb.com/t/how-does-scylladb-find-the-node-containing-the-data-i-want/161 "2022-12-11T07:53:10Z")
The driver can connect to any Scylla node and perform a query. That node will be designated as the coordinator node for the given query. The coordinator node can be the replica node (the one holding the data), but it doe… --- ## [ScyllaDB Version Upgrade](https://forum.scylladb.com/t/scylladb-version-upgrade/49)
**Author:** [@Guy](https://forum.scylladb.com/u/Guy)\ **Replies:** 1\ **Last updated:** [November 9, 2022, 10:42am UTC](https://forum.scylladb.com/t/scylladb-version-upgrade/49 "2022-11-09T10:42:27Z")
Can I upgrade from ScyllaDB Version X to version Y? --- ## [Experimental features](https://forum.scylladb.com/t/experimental-features/61)
**Author:** [@Anna](https://forum.scylladb.com/u/Anna)\ **Replies:** 0\ **Last updated:** [November 8, 2022, 8:53pm UTC](https://forum.scylladb.com/t/experimental-features/61 "2022-11-08T20:53:50Z")
Experimental features are still under development and are not stable enough to be used in production. Their design is not finalized, and their API will likely change, breaking backward or forward compatibility. Experimen… --- ## [ScyllaDB Monitoring has no data in the charts](https://forum.scylladb.com/t/scylladb-monitoring-has-no-data-in-the-charts/54)
**Author:** [@Guy](https://forum.scylladb.com/u/Guy)\ **Replies:** 0\ **Last updated:** [November 7, 2022, 10:17am UTC](https://forum.scylladb.com/t/scylladb-monitoring-has-no-data-in-the-charts/54 "2022-11-07T10:17:05Z")
The most common reason for seeing no data about your cluster after installing the ScyllaDB Monitoring stack is an issue with the connection to Prometheus. To check this: Login to the Prometheus console by pointing your… --- ## [How do you use ScyllaDB with Spring Boot?](https://forum.scylladb.com/t/how-do-you-use-scylladb-with-spring-boot/56)
**Author:** [@cynthia.dunlop](https://forum.scylladb.com/u/cynthia.dunlop)\ **Replies:** 0\ **Last updated:** [November 7, 2022, 2:07pm UTC](https://forum.scylladb.com/t/how-do-you-use-scylladb-with-spring-boot/56 "2022-11-07T14:07:47Z")
This blog explains how to use Spring Boot apps with ScyllaDB for time series data, taking advantage of shard-aware drivers and prepared statements: Using Spring Boot, ScyllaDB and Time Series Data - ScyllaDB --- ## [When to use filtering - and when not](https://forum.scylladb.com/t/when-to-use-filtering-and-when-not/55)
**Author:** [@cynthia.dunlop](https://forum.scylladb.com/u/cynthia.dunlop)\ **Replies:** 0\ **Last updated:** [November 7, 2022, 1:53pm UTC](https://forum.scylladb.com/t/when-to-use-filtering-and-when-not/55 "2022-11-07T13:53:15Z")
Sometimes you want to be able to query by different columns, but you’re not interested in creating secondary indexes. Filtering is one more way of allowing such queries. The mechanism is really simple – the coordinator w… --- ## [I’m having performance issues. What should I do?](https://forum.scylladb.com/t/i-m-having-performance-issues-what-should-i-do/53)
**Author:** [@Guy](https://forum.scylladb.com/u/Guy)\ **Replies:** 0\ **Last updated:** [November 7, 2022, 7:47am UTC](https://forum.scylladb.com/t/i-m-having-performance-issues-what-should-i-do/53 "2022-11-07T07:47:41Z")
ScyllaDB auto-tunes for optimal performance, however, users still need to apply best practices in order to get the most out of their ScyllaDB deployments. Lower than expected performance can be a result of many factors,… --- ## [ScyllaDB is using up all of my memory. What’s going on?](https://forum.scylladb.com/t/scylladb-is-using-up-all-of-my-memory-what-s-going-on/50)
**Author:** [@Guy](https://forum.scylladb.com/u/Guy)\ **Replies:** 0\ **Last updated:** [November 6, 2022, 6:22am UTC](https://forum.scylladb.com/t/scylladb-is-using-up-all-of-my-memory-what-s-going-on/50 "2022-11-06T06:22:13Z")
ScyllaDB is designed to use all the memory it has and to put it to good use. Most notably to cache data. By default, when ScyllaDB starts up, it inspects the node’s hardware configuration and claims all memory to itself,… --- ## [What's the best way to count / scan a table in ScyllaDB? (full table scan)](https://forum.scylladb.com/t/whats-the-best-way-to-count-scan-a-table-in-scylladb-full-table-scan/48)
**Author:** [@Tomersan](https://forum.scylladb.com/u/Tomersan)\ **Replies:** 0\ **Last updated:** [November 4, 2022, 6:36pm UTC](https://forum.scylladb.com/t/whats-the-best-way-to-count-scan-a-table-in-scylladb-full-table-scan/48 "2022-11-04T18:36:11Z")
If you wish to perform a full table scan, please look into the following blog posts on how to do an efficient full table scan: The theory behind an efficient full table scan Blog by Avi (our CTO) Follow up Blog with co… --- ## [How many connections should I open from each ScyllaDB client application?](https://forum.scylladb.com/t/how-many-connections-should-i-open-from-each-scylladb-client-application/43)
**Author:** [@Guy](https://forum.scylladb.com/u/Guy)\ **Replies:** 0\ **Last updated:** [November 3, 2022, 1:25pm UTC](https://forum.scylladb.com/t/how-many-connections-should-i-open-from-each-scylladb-client-application/43 "2022-11-03T13:25:41Z")
As a rule of thumb, for Scylla’s best performance, each client needs at least 1-3 connections per Scylla core. For example, in a cluster with three nodes, each node with 16 cores, each client application should open 32 (… --- ## [What is the difference between Clustering, Primary, Partition, and Composite (or Compound) Keys in ScyllaDB?](https://forum.scylladb.com/t/what-is-the-difference-between-clustering-primary-partition-and-composite-or-compound-keys-in-scylladb/41)
**Author:** [@Guy](https://forum.scylladb.com/u/Guy)\ **Replies:** 0\ **Last updated:** [November 2, 2022, 11:04am UTC](https://forum.scylladb.com/t/what-is-the-difference-between-clustering-primary-partition-and-composite-or-compound-keys-in-scylladb/41 "2022-11-02T11:04:26Z")
In ScyllaDB (and Apache Cassandra for that matter) A Primary Key is defined within a table. It is one or more columns used to identify a row. All tables must include a definition for a Primary Key. For example, in the ta…