Got full marks here which felt good, but I'd be lying if I said I wasn't surprised.
Start by clarifying the problem and constraints, then define the DP state and recurrence relation. Walk through a small example to validate your approach, and finally discuss time and space complexity and possible optimizations.
Pro tip: Amazon values working backwards from the customer, so relate the problem to real-world scenarios like text processing or data validation. Also, mention edge cases and how you'd test your solution.
Ask clarifying questions to ensure you understand the input, output, and constraints. Identify if it's a classic DP problem like edit distance, longest common subsequence, or palindrome partitioning.
Clearly state what each DP cell represents, such as dp[i][j] for substrings or prefixes. Explain how the state captures the necessary information to solve subproblems.
Derive the transition between states, considering all possible choices (e.g., match, insert, delete, replace). Ensure the recurrence covers base cases and handles edge conditions.
Write pseudocode or code, then analyze time and space complexity. Discuss potential optimizations like using 1D arrays or memoization to reduce space.
Walk through a small example to verify correctness, and consider edge cases like empty strings or large inputs. Mention how you would test the solution.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Start by clarifying requirements (e.g., stateless JWT vs session-based, integration with existing user store) and then outline a layered Spring Security configuration. Walk through the implementation from dependencies and security config to token generation, validation, and endpoint protection, emphasizing trade-offs and production concerns.
Pro tip: At Amazon, always tie your design to scalability and operational excellence—mention how your auth solution handles horizontal scaling, token revocation, and monitoring, and be ready to discuss why you chose JWT over sessions (or vice versa) in terms of statelessness and latency.
Ask about authentication type (JWT, OAuth2, session), user store (DB, LDAP, Cognito), and non-functional needs like scalability and compliance. This ensures your solution aligns with the interviewer's expectations.
Describe the components: Spring Security filter chain, authentication provider, token service, and user details service. Explain how requests flow through filters for authentication and authorization.
Walk through adding dependencies (spring-boot-starter-security, jjwt), configuring SecurityFilterChain, implementing UserDetailsService, and creating endpoints for login and token refresh. Show code snippets or pseudocode for key parts.
Discuss pros/cons of JWT vs sessions, token revocation strategies, handling token expiration, and securing sensitive endpoints. Mention how to scale stateless auth and integrate with API Gateway.
Recap the solution, emphasizing security best practices (HTTPS, password hashing, secret management) and operational aspects (logging, metrics, rate limiting).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.