Saga pattern for distributed transactions in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of the Saga pattern in distributed systems?

Choose the best explanation for why the Saga pattern is used in distributed transactions.

A To replicate data synchronously between microservices for consistency.

B To batch multiple requests into one to reduce network calls.

C To coordinate a sequence of local transactions across services with compensating actions on failure.

D To ensure all distributed services commit or rollback changes atomically like a single database transaction.

💡 Hint

Think about how distributed systems handle failures without locking resources.

The Saga pattern breaks a distributed transaction into a series of local transactions with compensating actions to undo changes if a step fails, avoiding the need for distributed locks.

❓ Architecture

intermediate

Which component is essential in a Saga orchestration-based architecture?

Identify the key component responsible for managing the sequence of transactions and compensations in an orchestration-based Saga.

A A load balancer that routes requests to different microservices.

B A distributed event bus that broadcasts events without central control.

C A shared database that all services use to coordinate commits.

D A centralized Saga orchestrator that commands each service to execute or compensate transactions.

💡 Hint

Consider which part controls the flow of the Saga steps explicitly.

In orchestration-based Saga, a central orchestrator directs each service when to perform its transaction or compensation, managing the Saga flow.

❓ scaling

advanced

How does the Saga pattern help improve scalability compared to distributed two-phase commit (2PC)?

Choose the best explanation of how Saga supports scalability in distributed systems.

A Saga avoids locking resources across services, allowing independent progress and reducing bottlenecks.

B Saga uses synchronous blocking calls to ensure all services commit simultaneously.

C Saga requires a global lock on all services to maintain consistency.

D Saga replicates all data to a central node to speed up transactions.

💡 Hint

Think about how locking affects system throughput and concurrency.

Saga allows each service to commit its local transaction independently without waiting for others, avoiding distributed locks and improving scalability.

❓ tradeoff

advanced

What is a key tradeoff when using the Saga pattern for distributed transactions?

Identify the main downside of using Saga compared to traditional atomic transactions.

A Data consistency is eventually consistent, not strongly consistent during the transaction.

B It requires all services to share the same database schema.

C It guarantees immediate rollback of all changes on failure.

D It eliminates the need for compensating transactions.

💡 Hint

Consider how Saga handles failures and data visibility during the process.

Saga provides eventual consistency by using compensating transactions, so data may be temporarily inconsistent until all steps complete or compensate.

❓ estimation

expert

Estimate the number of compensating transactions needed if a Saga with 5 steps fails at step 4.

A Saga consists of 5 sequential local transactions. If the transaction fails at step 4, how many compensating transactions must be executed to rollback?

A 4 compensating transactions

B 3 compensating transactions

C 5 compensating transactions

D 1 compensating transaction

💡 Hint

Think about which steps have already committed before failure and need compensation.

If failure occurs at step 4, steps 1, 2, and 3 have committed and require compensation. Step 4 did not commit, so no compensation needed for it.