When designing the backend of a crypto exchange, selecting the right database architecture is crucial. Two common NoSQL databases often considered for this type of application are Amazon DynamoDB and Apache Cassandra. Both offer horizontal scalability and high availability, but they shine in different use cases. This post explores their differences using concrete examples from the crypto exchange world.

DynamoDB: Ideal for On-Ramp and Off-Ramp Workflows

Use Case: A crypto exchange managing user flows from fiat to crypto (on-ramp) and from crypto to fiat (off-ramp).

DynamoDB is a fully managed NoSQL database provided by AWS. It’s designed for low-latency read/write operations and integrates seamlessly with other AWS services like Lambda, Step Functions, and API Gateway. These characteristics make it a perfect match for workflows such as:

• KYC/KYB processing
• Payment gateway integrations (credit cards, bank transfers)
• Transaction state updates
• Account balance adjustments
• Real-time status tracking for deposits and withdrawals

Since these operations are often part of event-driven architectures or serverless applications, DynamoDB’s automatic scaling and consistent performance under unpredictable load become major advantages. You don’t need to manage infrastructure or worry about capacity planning.

Why DynamoDB fits here:

• Predictable millisecond latency
• Automatic scaling during peak activity (e.g., market surges)
• Tight integration with AWS services used in modern payment flows
• Built-in support for TTL, conditional writes, and strongly consistent reads when needed

Cassandra: Best for Globally Distributed User Activity

Use Case: A crypto exchange managing a globally distributed support system with user tickets, logs, and activity tracking.

Apache Cassandra is a distributed, peer-to-peer database designed for high-volume write workloads across multiple regions. It’s commonly used by companies like Netflix and Apple for globally available systems that cannot afford downtime or central points of failure.

For a crypto exchange operating at scale, Cassandra is ideal for systems like:

• Distributed customer support ticket tracking
• Logging and auditing user actions (logins, trades, API calls)
• Global analytics of user behavior
• Event stores for internal alerting or fraud detection

Cassandra’s masterless architecture means any node can accept reads and writes, and data is automatically replicated across the cluster. This design ensures that user data is available even if a data center goes down—critical for global operations.

Why Cassandra fits here:

• High availability with no single point of failure
• Tunable consistency levels depending on the use case
• Massive write throughput for activity logs and user-generated data
• Natural fit for multi-region deployments

Summary

Feature	DynamoDB	Cassandra
Management	Fully managed by AWS	Self-managed or managed service (e.g., Astra DB)
Use Case Example	On-ramp / Off-ramp transaction processing	Distributed user ticket and activity tracking
Scaling	Auto-scaling (on-demand or provisioned)	Manual scaling by adding/removing nodes
Availability	Multi-AZ, high availability via AWS infrastructure	Multi-region, peer-to-peer, fault-tolerant architecture
Latency	Very low and consistent	Low, but may vary depending on topology
Integration	Deep AWS integration (Lambda, Step Functions, etc.)	Integrates well with Spark, Kafka, and data platforms
Cost	Pay-per-use; can grow expensive at scale	Free software, but operational overhead is significant

Final Thoughts

The choice between DynamoDB and Cassandra depends on your priorities. If you’re building a crypto platform with AWS-native components and want to focus on quick deployment and predictable performance, DynamoDB is a strong choice for operational workflows like deposits, withdrawals, and transaction states.

If your system needs to handle global scale, write-heavy workloads, and you require full control over replication and data locality, then Cassandra is a better fit for backend systems like support platforms, logging infrastructure, or real-time analytics.