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Fully managed, serverless Apache Cassandra-compatible database — no clusters to manage, infinite scale on demand
Amazon Keyspaces (for Apache Cassandra) is a scalable, highly available, fully managed serverless database service that is compatible with Apache Cassandra. It lets you run Cassandra workloads on AWS using the same Cassandra Query Language (CQL), drivers, and developer tools you already use — without managing servers, software, or capacity. Keyspaces automatically scales tables up and down based on actual application traffic and replicates data three times across multiple Availability Zones for durability.
Migrate or build Apache Cassandra-compatible workloads on a fully managed, serverless AWS database that eliminates operational overhead while providing single-digit millisecond performance at any scale.
Use When
Avoid When
Serverless — no cluster management
No EC2 instances, no Cassandra ring topology to manage. AWS handles all infrastructure.
Apache Cassandra CQL compatibility
Use existing CQL drivers (v3, v4), tools, and application code with minimal changes.
On-demand capacity mode
Pay per request; automatically scales to handle any traffic level without pre-provisioning.
Provisioned capacity mode
Specify RCUs and WCUs for predictable workloads; supports auto-scaling policies.
Auto-scaling (provisioned mode)
Define min/max RCU/WCU and target utilization; Keyspaces adjusts capacity automatically.
Multi-AZ replication (3 AZs)
Data is automatically replicated across three AZs in a Region — no configuration required.
Point-in-time recovery (PITR)
Continuous backups with restore to any second in the last 35 days.
On-demand backups
Manual backups retained until explicitly deleted; no performance impact.
Encryption at rest (AWS KMS)
Default AWS-owned keys or customer-managed KMS keys (CMKs) supported.
Encryption in transit (TLS)
All data in transit is encrypted using TLS. Required by default.
TTL (Time to Live)
Column-level or row-level TTL; expired data is automatically deleted. Affects per-operation column limits.
VPC endpoints (AWS PrivateLink)
Access Keyspaces from within a VPC without traversing the public internet.
IAM authentication
Use IAM roles and policies for fine-grained access control instead of Cassandra-native auth.
AWS CloudTrail integration
All API calls logged to CloudTrail for audit and compliance.
Amazon CloudWatch metrics
Built-in metrics for read/write throughput, latency, errors, and system health.
Lightweight transactions (LWT)
Supports IF NOT EXISTS and IF conditions for conditional writes — with performance cost.
Secondary indexes
Up to 10 per table; allow queries on non-partition-key columns.
Multi-Region replication
Keyspaces does not natively support multi-Region replication like DynamoDB Global Tables. This is a key differentiator in exam scenarios.
Transactions (ACID multi-row)
No multi-row ACID transactions. Logged batches provide atomicity for a batch but are not full ACID transactions.
SQL queries / JOINs
CQL only — no SQL JOINs, subqueries, or GROUP BY aggregations across tables.
Cost Visibility and Optimization
high freqUse AWS Cost Explorer to analyze Keyspaces spending by capacity mode (on-demand vs provisioned), identify tables with low utilization, and right-size provisioned capacity. Tag Keyspaces tables with cost allocation tags to enable per-application cost breakdown in Cost Explorer.
Operational Best Practices and Cost Checks
high freqTrusted Advisor checks can surface underutilized provisioned capacity in Keyspaces tables, recommending a switch to on-demand mode or reduced provisioned throughput to reduce costs. Relevant for SAA-C03 cost-optimization domain questions.
Granular Cost Allocation and Chargeback
high freqAWS Cost and Usage Reports (CUR) provide the most granular billing data for Keyspaces, including per-table usage broken down by storage, read units, and write units. Used by finance teams for chargeback and showback models.
Budget Alerting for Serverless Databases
high freqSet AWS Budgets alerts on Keyspaces service costs to prevent bill shock from unexpected traffic spikes in on-demand mode. Combine with CloudWatch alarms on ConsumedReadCapacityUnits and ConsumedWriteCapacityUnits metrics for proactive monitoring.
Capacity Mode Recommendations
high freqAWS Compute Optimizer analyzes Keyspaces table usage patterns and recommends whether to use provisioned or on-demand capacity mode, and what provisioned throughput values to set — reducing over-provisioning costs without sacrificing performance.
Serverless Event-Driven Data Processing
medium freqLambda functions triggered by EventBridge, SQS, or Kinesis write processed records into Keyspaces tables using the CQL driver over TLS. Full serverless architecture with no infrastructure to manage end-to-end.
Real-Time IoT / Telemetry Ingestion
medium freqKinesis Data Streams ingests high-velocity IoT or clickstream data; Lambda consumers process and write records into Keyspaces for low-latency lookups. Common pattern for time-series data at scale.
Cassandra to Keyspaces Migration
medium freqDMS supports migrating data from self-managed Apache Cassandra clusters to Amazon Keyspaces. Used in SAP-C02 workload migration scenarios — Keyspaces is the managed target, DMS handles the data movement.
Performance Monitoring and Alerting
medium freqCloudWatch provides built-in metrics for Keyspaces including SuccessfulRequestLatency, ConsumedReadCapacityUnits, ConsumedWriteCapacityUnits, and SystemErrors. Set alarms to detect throttling events and trigger auto-scaling or operational responses.
Private VPC Connectivity
medium freqUse VPC endpoints powered by AWS PrivateLink to connect applications running in a VPC to Keyspaces without routing traffic through the public internet — required for compliance-sensitive workloads and a common exam scenario for security-conscious architectures.
The row size limit is 1 MB — NOT 4 MB. The 4 MB limit applies to logged batches, not individual rows. These two values are intentionally confused in exam questions.
When a logged batch contains static columns, the maximum number of statements drops from 100 to 50. If an exam question mentions 'static columns' in a batch context, the answer is 50, not 100.
TTL configuration directly affects per-operation column count limits. Without TTL: 225 columns max per INSERT/UPDATE. With TTL enabled: 112 columns max. This is a tested detail — do not assume TTL is only about data expiration.
Row size limit = 1 MB (NOT 4 MB). The 4 MB limit is for logged batches. These two values are swapped in exam distractors — know which limit applies to which construct.
Static columns in a logged batch reduce the statement limit from 100 to 50. Any exam question mentioning 'static columns' in a batch context is testing this specific sub-limit.
TTL reduces the maximum columns per INSERT/UPDATE from 225 to 112. TTL is not just a data expiration feature — it directly impacts per-operation column count limits.
Amazon Keyspaces does NOT support multi-Region replication (unlike DynamoDB Global Tables). If a question asks for a globally distributed, multi-Region, low-latency NoSQL solution with Cassandra compatibility, note this limitation and consider whether the architecture needs a workaround.
Keyspaces uses IAM for authentication — NOT Cassandra's native username/password auth. In exam scenarios about securing Keyspaces access, the answer involves IAM roles and policies, not Cassandra credentials.
PITR (Point-in-Time Recovery) in Keyspaces has a 35-day retention window — the same as DynamoDB. If a question asks about recovering from accidental data deletion in Keyspaces within the last month, PITR is the correct answer.
For cost optimization questions (SAA-C03 domain), remember: on-demand mode is best for unpredictable or spiky workloads; provisioned mode with auto-scaling is best for steady, predictable traffic. AWS Cost Explorer, Trusted Advisor, and Compute Optimizer all appear in Keyspaces cost-optimization exam scenarios.
Keyspaces data is automatically replicated across THREE Availability Zones within a Region. This is built-in and requires no configuration — relevant for availability and durability questions.
Static data per partition is capped at 1 MB — the same number as the row size limit but a completely different constraint. Three separate '1 MB' limits exist: row size, static data per partition. The 4 MB limit is only for logged batches.
In SAP-C02 migration scenarios, AWS DMS can migrate self-managed Apache Cassandra workloads to Amazon Keyspaces. Keyspaces is the recommended modernization target for Cassandra on AWS — no code changes needed if using CQL drivers.
Common Mistake
The row size limit in Amazon Keyspaces is 4 MB
Correct
The row size limit is 1 MB. The 4 MB limit applies to logged batch statements, not individual rows.
This is the #1 most tested misconception in Keyspaces exam questions. The 4 MB number is real but belongs to a different limit (logged batch size). Always ask: is the question about a single row or a batch? Row = 1 MB; Logged batch = 4 MB.
Common Mistake
A logged batch in Keyspaces can always contain up to 100 statements regardless of column types
Correct
The 100-statement limit applies to general logged batches. If the batch involves static columns, the limit drops to 50 statements.
Exam questions deliberately introduce the phrase 'static columns' to test whether you know this sub-limit. The presence of static columns in a batch is a signal that the answer should be 50, not 100. Memorize: static columns = half the batch statement limit.
Common Mistake
Enabling TTL on an INSERT or UPDATE operation has no effect on how many columns can be included in that operation
Correct
TTL directly reduces the maximum columns per INSERT/UPDATE from 225 (without TTL) to 112 (with TTL enabled).
Candidates treat TTL as purely a data lifecycle feature and do not associate it with operational limits. On the exam, if TTL is mentioned alongside a column count question, the answer changes. Remember: TTL ≈ halves the per-operation column count (225 → 112).
Common Mistake
Amazon Keyspaces supports multi-Region replication like DynamoDB Global Tables
Correct
Keyspaces does NOT natively support multi-Region replication. Data is replicated across three AZs within a single Region only.
DynamoDB Global Tables is a frequent comparison point. If an exam question requires active-active multi-Region NoSQL, DynamoDB is the answer — not Keyspaces. This distinction is especially tested in SAP-C02 architecture design questions.
Common Mistake
The 1 MB static data per partition limit and the 1 MB row size limit are the same thing
Correct
They are two separate limits that happen to share the same value. Row size limits a single row to 1 MB. Static data per partition limits the aggregate static column data within one partition to 1 MB.
Having two different limits with the same value (1 MB) creates confusion. Exam questions may describe a scenario where one limit is hit but not the other. Understand what each limit governs: row size = one row's total data; static data per partition = aggregate static columns across all rows in a partition.
Common Mistake
Amazon Keyspaces uses Cassandra's native username/password authentication
Correct
Keyspaces uses AWS IAM for authentication. You use IAM roles, users, and policies — not Cassandra-native credentials.
Developers migrating from self-managed Cassandra expect the same auth model. On the exam, security questions about Keyspaces always point to IAM, not Cassandra credentials. This also means you can use IAM conditions, SCPs, and resource-based policies for fine-grained access control.
ROW = 1 MB, BATCH = 4 MB, STATIC BATCH = 50 stmts, GENERAL BATCH = 100 stmts — 'One Row, Four Batches, Fifty Static, Hundred General' → 1-4-50-100
TTL HALVES: Without TTL = 225 columns; With TTL = ~112 columns (half). Think: 'TTL Takes half your columns away'
Keyspaces = 3 AZs in 1 Region. DynamoDB Global Tables = Multiple Regions. 'Keyspaces stays home; DynamoDB goes global'
For cost optimization in exam questions, remember the AWS Cost Quartet: Cost Explorer + Trusted Advisor + Cost and Usage Reports + Compute Optimizer — all four appear in Keyspaces cost scenarios
CertAI Tutor · SAA-C03, SAP-C02, DEA-C01 · 2026-02-21
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