Transitioning into senior roles at top product companies requires a shift from being a "task executor" to an "engineering leader." This roadmap is designed for the Senior Full-Stack Developer—balancing Java/Spring Boot depth, React frontend expertise, robust system design, and the operational rigor of CI/CD.

1. The 12-Week Strategic Roadmap

Phase	Duration	Focus Area
1	Weeks 1-2	DSA & Optimization: Patterns over memorization.
2	Weeks 3-4	Core Java Deep-Dive: JVM, Concurrency, and Java 8+.
3	Week 5	Spring Boot Mastery: Ecosystem, Security, and Transactions.
4	Week 6	Microservices: Resiliency, Event-Driven, and Scalability.
5	Week 7	System Design: Architectural patterns & trade-offs.
6	Week 8	SQL & Databases: Query optimization and advanced modeling.
7	Week 9	AWS Infrastructure: Cloud-native deployment components.
8	Week 10	DevOps: Kubernetes, Docker, and CI/CD automation.
9	Week 11	Low-Level Design (LLD): Patterns, SOLID, and Clean Code.
10	Week 12	Behavioral: Engineering maturity and leadership stories.

2. Core Technical Content

Phase 1: Data Structures & Algorithms

Focus on these 100 high-impact problems categorized by pattern:

Arrays (20): Two Sum, Buy/Sell Stock, Max Subarray, Product Except Self, Container With Most Water, 3Sum, Trapping Rain Water.
Strings (15): Longest Substring, Valid Palindrome, Group Anagrams, Minimum Window Substring.
HashMap/HashSet (15): Frequency mapping, Duplicate detection, TopK.
Linked List (10): Reverse, Merge, Detect Cycle, LRU Cache.
Stack/Queue (10): Valid Parentheses, Min Stack, Daily Temps.
Trees (15): Level Order, LCA, Diameter, Validate BST, Right Side View.
Graphs (10): Islands, Clone Graph, Course Schedule, Word Ladder.
Binary Search (10): Rotated Search, Koko Eating Bananas.
Dynamic Programming (15): Climbing Stairs, House Robber, Coin Change, Edit Distance.

Phase 2: Core Java

OOP: SOLID, Composition vs. Inheritance.
Collections: HashMap/ConcurrentHashMap internals.
Multithreading: ExecutorService, CompletableFuture, Virtual Threads (Java 21).
JVM: GC (G1/ZGC), Heap/Stack/Metaspace, JIT.

Phase 3-4: Backend & Microservices

Spring Boot: Bean lifecycle, AOP, Security (OAuth2/JWT), Async Processing.
Microservices: API Gateway, Service Discovery, Circuit Breakers (Resiliency), Saga Pattern, Event Sourcing, CQRS.

Phase 5: System Design

Core Concepts: CAP Theorem, Load Balancing, Sharding, Consistent Hashing, CDN.
Design Case Studies: URL Shortener, WhatsApp, Netflix, Uber, Payment Gateway, Inventory System.

Phase 6-9: Databases, AWS, & DevOps

SQL: Window Functions, CTEs, Indexing, Query Tuning.
AWS: EC2, S3, IAM, VPC, Lambda, EKS/ECS, RDS.
Kubernetes & Docker: Pods, Deployments, Ingress, Helm, Autoscaling.

Phase 11: Low-Level Design (LLD)

Implement: Parking Lot, Chess, Splitwise, Snake & Ladder, BookMyShow.
Focus: Design Patterns, SOLID Principles, UML, Clean Code standards.

3. Behavioral Excellence (Phase 10)

Prepare stories using the STAR method for:

Biggest production issue and resolution.
Leading a migration or technical decision.
Handling interpersonal conflict or mentoring junior engineers.
Reflecting on failures and lessons learned.

4. The Daily "Elite" Study Plan (3 Hours)

45 min: DSA (1–2 problems using patterns, not random guessing).
45 min: Core Java / Spring Boot deep dive.
45 min: System Design study.
30 min: SQL + AWS/DevOps concepts.
15 min: Behavioral interview prep (story reflection).

5. Structured 90-Day Bootcamp

I can mentor you through this. By adhering to this plan, you will cover:

180+ coding problems.
500+ Java/Spring interview questions.
30+ system design case studies.
100+ SQL questions.

Your Goal: Prioritize consistent daily practice over bursts of effort. Focus on understanding the "Why" behind every architectural choice—this is what separates a senior engineer from the rest.