What is the Alternative to Eventual Consistency?

The alternative to Eventual Consistency is Immediate Consistency, also known as Strong Consistency. In a system with immediate consistency, updates are immediately visible to all clients as soon as they are made. This means that once a write operation completes, all subsequent read operations will reflect that write’s updated state. This approach ensures that all clients see the same, consistent view of the data at all times, but it can introduce higher latency and lower availability compared to systems that use eventual consistency.

Use Cases of Strong Consistency

Strong consistency is typically used in scenarios where data integrity and consistency are paramount, even at the expense of increased latency or reduced availability. Here are some common use cases for strong consistency:

• Financial Transactions: Banking systems and payment processors require strong consistency to ensure that transactions are processed correctly and that account balances are always accurate.
• Healthcare Systems: Electronic health records (EHRs) and medical information systems need strong consistency to ensure that patient data is always up-to-date and accurate.
• E-commerce Checkout: During the checkout process on an e-commerce website, strong consistency is necessary to ensure that items in a shopping cart are correctly reflected in the final order.
• Reservation Systems: Systems that handle reservations for flights, hotels, or other services need strong consistency to prevent double bookings and ensure that reservations are processed correctly.
• Legal and Regulatory Compliance: Industries that must comply with strict legal and regulatory requirements, such as financial services or healthcare, often require strong consistency to ensure data accuracy.
• Real-time Collaboration: Applications that require real-time collaboration, such as collaborative editing tools or multiplayer games, benefit from strong consistency to maintain a consistent state across all participants.
• Critical Infrastructure: Systems that control critical infrastructure, such as power grids or transportation systems, often require strong consistency to ensure the safety and reliability of the infrastructure.

In these use cases, strong consistency is necessary to maintain data integrity and ensure that all users and systems see a consistent view of the data, even in the presence of concurrent updates and network partitions.