Reduce deploy-time backend latency via lazy Spring initialization

[Copilot]

✨ Enhancement

Deployment under active load triggered a response-time spike driven by Spring Boot cold start (~35–37s) during rolling replacement, while request traffic remained healthy (2xx). This PR applies a startup optimization in backend runtime config to reduce cold-start overhead without changing API behavior.

• What does this improve?

  • Reduces backend startup work on deploy by enabling on-demand bean initialization.
  • Targets the deployment window latency spike observed on /api/cards* during revision rollout.

• Why is this valuable?

  • During rollout, effective serving capacity temporarily drops while a new replica boots.
  • Lower startup cost shortens the period where fewer ready replicas handle full traffic.

• Implementation approach:

  • Backend startup optimization
    • backend/src/main/resources/application.yml
    • Enabled:

      spring:
        main:
          lazy-initialization: true

  • Test-scope guardrail for deterministic repository bootstrap
    • backend/src/test/java/com/threeriversbank/repository/CreditCardRepositoryTest.java
    • Scoped override to keep JPA test initialization eager:

      @DataJpaTest(properties = "spring.main.lazy-initialization=false")

[yortch]

@copilot check there are no thread.sleep delays introduced recently and remove them. I don't need these new changes suggested, please rever them.

[Copilot]

@copilot check there are no thread.sleep delays introduced recently and remove them. I don't need these new changes suggested, please rever them.

Addressed in commit 44ddf5f. I reverted the lazy-initialization changes and removed the Thread.sleep delay from CreditCardService#getAllCreditCards(). I also verified there are no Thread.sleep calls remaining under backend/src/main/java.

[Copilot]

Pull request overview

This PR currently removes an artificial random delay from the backend credit card listing path, improving /api/cards response latency. However, the implementation does not match the described lazy Spring initialization startup optimization.

Changes:

• Removed the random Thread.sleep from CreditCardService.getAllCreditCards().

Show a summary per file

File	Description
backend/src/main/java/com/threeriversbank/service/CreditCardService.java	Removes artificial request-path latency from the all-cards service method.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1