CASSANDRA Cheat Sheet 2026

The 30 highest-yield CASSANDRA facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. A developer wants to transition from a relational DBA role to a Cassandra DBA. What is the most important mindset shift required? → Replacing transactions with eventual consistency and query-first design
2. In Cassandra, what is a 'wide partition' and why is it a potential problem? → A partition with many rows that can cause memory pressure and slow reads
3. What is the effect of setting 'WITH LOGIN = false' when creating or altering a Cassandra role? → The role cannot be used to open a client connection to Cassandra
4. Which Cassandra-specific skill is most valued when joining a team that already has a large production cluster? → Diagnosing performance issues using nodetool and system tables
5. Which Cassandra metric indicates that a node is receiving more writes than it can process? → High MutationStage pending tasks in tpstats
6. What is the 'sstableloader' tool used for in Cassandra? → Bulk-loading existing SSTable files into a running Cassandra cluster
7. What is the purpose of 'incremental_backups' in Cassandra? → Copies each new SSTable to a backups/ subdirectory after it is flushed from MemTable
8. What role does the CommitLog play in Cassandra's write path? → It provides durability by recording every write before the MemTable
9. What Cassandra version do you use? → 3.9
10. Which `nodetool` command shows you the token ranges and replica ownership for your cluster? → nodetool ring
11. When should you use a Cassandra Materialized View instead of a denormalized table? → When you need Cassandra to automatically maintain a read-optimized copy of a base table
12. A team is adopting Cassandra for the first time. What is the best first project to maximize learning with manageable risk? → Start with a non-critical append-only use case like event logging or audit trails
13. What is the purpose of the `nodetool repair` command in Cassandra? → Synchronizes replicas to fix inconsistencies
14. What availability risk is introduced by leaving the system_auth keyspace at its default replication factor of 1? → A single node failure can make authentication unavailable cluster-wide
15. What does the 'nodetool snapshot' command create? → A full backup by hard-linking current SSTable files into a snapshot directory
16. Which nodetool command triggers a full repair to synchronize data across all replicas for a keyspace? → nodetool repair
17. What is the primary data distribution mechanism in Apache Cassandra? → Consistent hashing with a token ring
18. Which internal Cassandra component stores recently written data in memory before flushing to disk? → Memtable
19. Cassandra was created by who? → Facebook
20. Which tool is employed to view a table's statistics? → Nodetool
21. In Cassandra CQL, what does the TTL function return when called on a column value? → The number of seconds remaining before the cell expires
22. In Cassandra data modeling, what is 'denormalization'? → Storing duplicate data in multiple tables to support different query patterns efficiently
23. What is a user-defined type (UDT) in Cassandra CQL? → A named group of typed fields that can be embedded as a column value in a table
24. What is the purpose of 'gc_grace_seconds' in Cassandra? → The period tombstones must persist before being eligible for deletion during compaction
25. What is the purpose of a secondary index in Cassandra? → To allow queries on non-primary-key columns without needing ALLOW FILTERING
26. By "Table in Cassandra," what do you mean? → Column-Family
27. What does the 'endpoint_snitch' configuration control in Cassandra? → How Cassandra determines the topology (rack/DC) of nodes for replica placement
28. How do you safely perform a rolling upgrade of a Cassandra cluster? → Upgrade and restart one node at a time, verifying stability before proceeding to the next
29. What is an SSTable in Apache Cassandra? → An immutable on-disk file that stores sorted partition data
30. How do you enable authentication in Cassandra? → Set authenticator: PasswordAuthenticator in cassandra.yaml