Spring Boot Developer Interview Preparation Guide

In the default proxy-based mode, only calls passing through the proxy are intercepted. Self-invocation bypasses that boundary. Place the transactional operation behind the appropriate service boundary or choose an explicit transaction approach. Verify behavior with an integration test rather than relying on the annotation’s presence.

Check your understanding: Force a later write to fail and verify earlier writes roll back.

Common trap: Assuming the annotation changes every internal method call.

Concept reference: Spring: declarative transactions

Rollback behavior depends on the configured rules; default behavior distinguishes unchecked failures from checked exceptions. Define the intended policy for business and infrastructure failures, avoid swallowing errors inside the boundary, and test the actual configuration and database behavior.

Check your understanding: Trigger checked and unchecked failures against the intended transaction boundary.

Common trap: Adding broad exception handling that accidentally commits partial work.

Concept reference: Spring: declarative transactions

Use realistic request identities and verify authorization for the target resource, not only a successful response for an administrator. Test absent credentials, wrong ownership, malformed input and a dependency failure. Keep a separate durable-data assertion for mutations so HTTP success is not the only evidence.

Check your understanding: Attempt to access another account’s record with a valid ordinary account.

Common trap: A controller test suite containing only happy-path administrator calls.

Concept reference: Playwright: reliable browser tests

First, identify technical constraints and define measurable service objectives. Next, follow a request across validation, business logic, storage and asynchronous work. Contrast architectural trade-offs across simplicity, correctness, maintainability and scale, explicitly mitigate the risk of queued work grows faster than it can be processed, and confirm system stability using queue-depth metrics, bounded retry behaviour and a recovery drill.

Common trap: Reaching for a specific library or framework before defining constraints, failure envelopes, and automated verification criteria.

Prioritise the failure mode exhibiting the highest user blast radius and lowest observability. Formulate an explicit containment boundary, implement idempotent retries with jitter, and establish an automated rollback threshold. Verify resilience through shadow-traffic comparison and an error-budget based cutover rule.

Common trap: Relying on passive monitoring dashboards without defining explicit error-budget alerts, rollback triggers, and verified recovery procedures.

Structure the response using Context-Decision-Tradeoff-Result: articulate the business and technical constraints, compare viable alternatives, explain the implementation (follow a request across validation, business logic, storage and asynchronous work), and document the accepted trade-off. Provide concrete proof: a project example, measured result and repeatable verification step.

Common trap: Speaking only in high-level abstractions or team accomplishments without detailing your direct implementation decisions, trade-offs, and measured results.

Formulate a falsifiable hypothesis from observable telemetry before altering configurations. Then correlate the request trace with transaction state, queue ownership and dependency budgets. Isolate the defect to the smallest reproducible boundary, validate root cause with evidence, and confirm full resolution using a compatibility test matrix and a staged rollout metric.

Common trap: Applying speculative fixes or restarting services blindly without establishing an observable signal connected to a falsifiable hypothesis.

Produce an idempotency test, failure trace and repeatable recovery runbook. Document baseline assumptions, technical mechanism (follow a request across validation, business logic, storage and asynchronous work), rejected alternatives, bounded failure envelopes, and deterministic pass criteria. Supply reproducible verification via load-test results, retry counts and a measured cost estimate.

Common trap: Presenting architecture diagrams or slides lacking automated unit/integration tests, observable metrics, or automated rollback configurations.