🚀 Spring Boot Complete Roadmap (2026)

A structured, phase-by-phase guide from beginner to production-grade microservices engineer.

📋 Table of Contents

Phase 1 – Spring Boot Fundamentals
Phase 2 – Intermediate (Professional API Developer)
Phase 3 – Advanced Spring Boot (Microservices Entry)
Phase 4 – Microservices Communication & Resilience
Phase 5 – Deployment & DevOps
Phase 6 – What's New & Often Missed (2026 Additions)
🏆 Final Project
📅 Suggested Timeline
🔥 Top Interview Questions

Phase 1 – Spring Boot Fundamentals

🎯 Goal: Understand how Spring Boot works and build CRUD REST APIs with SQL + NoSQL.

1.1 Introduction to Spring Boot

Learn:

What is Spring vs Spring Boot
Auto-configuration internals
Starter dependencies (spring-boot-starter-*)
Embedded servers: Tomcat, Jetty, Undertow
Convention over configuration

Build:

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String hello() {
        return "Hello, Spring Boot 2026!";
    }
}

1.2 Creating a Spring Boot Project

Learn:

Spring Initializr (start.spring.io)
Project structure (src/main/java, resources)
Maven vs Gradle
application.properties vs application.yml

Practice – Create project with:

Spring Web
Spring Data JPA
H2 (in-memory DB)

1.3 REST Controller Basics

Learn:

Annotation	Purpose
`@RestController`	Combines `@Controller` + `@ResponseBody`
`@RequestMapping`	Maps URL prefix
`@GetMapping`	Read
`@PostMapping`	Create
`@PutMapping`	Update
`@DeleteMapping`	Delete
`@PathVariable`	URL segment extraction
`@RequestParam`	Query param extraction
`@RequestBody`	Deserialize JSON body

Build CRUD API for: User · Product · Order

1.4 Database Integration – SQL

SQL (Mandatory):

H2 (in-memory for dev/testing)
MySQL / PostgreSQL (production)

Entity Mapping:

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false)
    private String name;

    @OneToMany(mappedBy = "user", cascade = CascadeType.ALL)
    private List<Order> orders;
}

Relationships: @OneToMany · @ManyToOne · @ManyToMany · @OneToOne

Repositories:

public interface UserRepository extends JpaRepository<User, Long> {
    @Query("SELECT u FROM User u WHERE u.email = :email")
    Optional<User> findByEmail(@Param("email") String email);
}

Build: E-commerce style CRUD app

1.5 NoSQL Integration (Optional but Recommended)

Choose one: MongoDB · Couchbase · Redis (as document store)

@Document(collection = "products")
public class Product {
    @Id
    private String id;
    private String name;
    private double price;
}

public interface ProductRepository extends MongoRepository<Product, String> {}

1.6 Profiles & Environment Config

# application-dev.yml
spring:
  datasource:
    url: jdbc:h2:mem:devdb

# application-prod.yml
spring:
  datasource:
    url: jdbc:postgresql://localhost/proddb

@Profile("dev")
@Bean
public DataLoader devDataLoader() { ... }

Activate via: --spring.profiles.active=dev

1.7 DevTools

Hot reload on classpath change
LiveReload browser plugin support
Automatic restart behavior

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <optional>true</optional>
</dependency>

1.8 Scheduling & Batch

@EnableScheduling
@SpringBootApplication
public class App { ... }

@Scheduled(cron = "0 0 * * * *")  // Every hour
public void runTask() { ... }

Spring Batch basics: Job → Step → ItemReader → ItemProcessor → ItemWriter

✅ After Phase 1 you can:

Build production-level CRUD APIs
Connect SQL & NoSQL databases
Use profiles for environments
Handle basic scheduling

Phase 2 – Intermediate (Professional API Developer Level)

🎯 Goal: Build secure, tested, and versioned APIs.

2.1 Exception Handling

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(ResourceNotFoundException.class)
    public ResponseEntity<ErrorResponse> handleNotFound(ResourceNotFoundException ex, HttpServletRequest request) {
        ErrorResponse error = new ErrorResponse(
            LocalDateTime.now(), 404, "Not Found", ex.getMessage(), request.getRequestURI()
        );
        return ResponseEntity.status(404).body(error);
    }
}

Standard Error Response:

{
  "timestamp": "2026-01-01T10:00:00",
  "status": 400,
  "error": "Bad Request",
  "message": "Validation failed",
  "path": "/api/users"
}

2.2 Spring Security

Basics:

Authentication vs Authorization
Basic Auth
Role-based access (ROLE_USER, ROLE_ADMIN)

Advanced:

@Configuration
@EnableWebSecurity
public class SecurityConfig {

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        http
            .csrf(csrf -> csrf.disable())
            .authorizeHttpRequests(auth -> auth
                .requestMatchers("/api/auth/**").permitAll()
                .anyRequest().authenticated()
            )
            .addFilterBefore(jwtFilter, UsernamePasswordAuthenticationFilter.class)
            .sessionManagement(s -> s.sessionCreationPolicy(STATELESS));
        return http.build();
    }
}

JWT Flow: Login → Generate Token → Attach to Header → Validate on Each Request

Password encoding:

@Bean
public PasswordEncoder passwordEncoder() {
    return new BCryptPasswordEncoder();
}

2.3 REST API Best Practices

HATEOAS: Add links to responses for discoverability
API Versioning strategies:

Strategy	Example
URI	`/api/v1/users`
Header	`X-API-Version: 1`
Parameter	`/api/users?version=1`
Media type	`Accept: application/vnd.app.v1+json`

Pagination & Sorting: Use Pageable with JpaRepository
DTOs: Never expose entities directly — use mapper layer (MapStruct recommended)

2.4 Testing

Unit Testing:

@ExtendWith(MockitoExtension.class)
class UserServiceTest {

    @Mock
    private UserRepository userRepository;

    @InjectMocks
    private UserService userService;

    @Test
    void shouldReturnUserById() {
        when(userRepository.findById(1L)).thenReturn(Optional.of(new User()));
        assertNotNull(userService.getUser(1L));
    }
}

Integration Testing:

@SpringBootTest
@AutoConfigureMockMvc
class UserControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    void shouldReturn200ForGetUsers() throws Exception {
        mockMvc.perform(get("/api/users"))
               .andExpect(status().isOk());
    }
}

Test: Controllers · Services · Repositories · Security filters

2.5 Actuator & Monitoring

management:
  endpoints:
    web:
      exposure:
        include: health,metrics,info,prometheus
  endpoint:
    health:
      show-details: always

Key endpoints: /actuator/health · /actuator/metrics · /actuator/prometheus

Integrate with Prometheus → visualize in Grafana

✅ After Phase 2 you can:

Build secure JWT-protected APIs
Write production-level tests
Monitor applications with Prometheus & Grafana

Phase 3 – Advanced Spring Boot (Microservices Entry)

🎯 Goal: Understand distributed systems basics.

3.1 Advanced Profiles

Environment-specific beans with @Profile
Profile-based config file loading
@ConditionalOnProperty for feature toggles

3.2 Spring Cloud Overview

Component	Purpose
Config Server	Centralized configuration
Eureka	Service discovery
Gateway	API routing
Cloud Bus	Config broadcasting
LoadBalancer	Client-side load balancing

3.3 Service Discovery (Eureka)

// Eureka Server
@EnableEurekaServer
@SpringBootApplication
public class EurekaServer { ... }

// Client Service
@EnableDiscoveryClient
@SpringBootApplication
public class UserService { ... }

# Client application.yml
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/

3.4 API Gateway

spring:
  cloud:
    gateway:
      routes:
        - id: user-service
          uri: lb://USER-SERVICE
          predicates:
            - Path=/api/users/**
          filters:
            - StripPrefix=1
            - name: RequestRateLimiter
              args:
                redis-rate-limiter.replenishRate: 10
                redis-rate-limiter.burstCapacity: 20

Features: Route predicates · Custom filters · Rate limiting · JWT validation at gateway

3.5 Centralized Config

# Config Server application.yml
spring:
  cloud:
    config:
      server:
        git:
          uri: https://github.com/your-org/config-repo

Refresh config dynamically: POST /actuator/refresh or via Spring Cloud Bus

Build – Microservices Project:

├── eureka-server        (port 8761)
├── config-server        (port 8888)
├── api-gateway          (port 8080)
├── user-service         (port 8081)
├── order-service        (port 8082)
└── product-service      (port 8083)

✅ After Phase 3: You understand microservices architecture basics.

Phase 4 – Microservices Communication & Resilience

🎯 Goal: Build production-grade distributed systems.

4.1 Inter-Service Communication

Synchronous:

// OpenFeign (preferred)
@FeignClient(name = "inventory-service")
public interface InventoryClient {
    @GetMapping("/api/inventory/{productId}")
    InventoryResponse checkStock(@PathVariable String productId);
}

Asynchronous: Kafka / RabbitMQ (see Event-Driven section)

4.2 Resilience4j

@CircuitBreaker(name = "inventoryService", fallbackMethod = "fallbackStock")
@Retry(name = "inventoryService")
@TimeLimiter(name = "inventoryService")
public CompletableFuture<InventoryResponse> checkInventory(String productId) {
    return CompletableFuture.supplyAsync(() -> inventoryClient.checkStock(productId));
}

public CompletableFuture<InventoryResponse> fallbackStock(String productId, Throwable t) {
    return CompletableFuture.completedFuture(new InventoryResponse(false));
}

Patterns: Circuit Breaker · Retry · Rate Limiter · Bulkhead · Time Limiter

4.3 Distributed Tracing

2026 Recommended Stack: Micrometer Tracing + Zipkin (Spring Cloud Sleuth is deprecated)

management:
  tracing:
    sampling:
      probability: 1.0
  zipkin:
    tracing:
      endpoint: http://localhost:9411/api/v2/spans

Every request gets a traceId and spanId propagated across services automatically.

4.4 Spring Cloud Bus

Broadcasts config refresh events across all instances
Backed by RabbitMQ or Kafka

# Trigger refresh across all services
POST /actuator/busrefresh

4.5 Event-Driven Architecture

// Producer (Order Service)
@Service
public class OrderService {
    @Autowired
    private KafkaTemplate<String, OrderEvent> kafkaTemplate;

    public void placeOrder(Order order) {
        kafkaTemplate.send("order-events", new OrderEvent(order.getId(), "PLACED"));
    }
}

// Consumer (Inventory Service)
@KafkaListener(topics = "order-events", groupId = "inventory-group")
public void handleOrderEvent(OrderEvent event) {
    inventoryService.reserveStock(event.getOrderId());
}

Supported brokers: Apache Kafka · RabbitMQ

✅ After Phase 4: You can build scalable distributed systems.

Phase 5 – Deployment & DevOps

🎯 Goal: Ship to production like a real company.

5.1 Docker

Dockerfile (multi-stage):

# Build stage
FROM maven:3.9-eclipse-temurin-21 AS builder
WORKDIR /app
COPY pom.xml .
RUN mvn dependency:go-offline
COPY src ./src
RUN mvn package -DskipTests

# Runtime stage
FROM eclipse-temurin:21-jre-alpine
WORKDIR /app
COPY --from=builder /app/target/*.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]

Docker Compose:

services:
  user-service:
    build: ./user-service
    ports: ["8081:8080"]
    environment:
      - SPRING_PROFILES_ACTIVE=docker
    depends_on: [postgres, kafka]
  postgres:
    image: postgres:16
    environment:
      POSTGRES_DB: userdb
      POSTGRES_PASSWORD: secret
  kafka:
    image: confluentinc/cp-kafka:latest

5.2 CI/CD

GitHub Actions workflow:

name: Build & Deploy
on:
  push:
    branches: [main]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-java@v4
        with: { java-version: '21', distribution: 'temurin' }
      - run: mvn test
      - run: mvn package -DskipTests
      - run: docker build -t myapp:${{ github.sha }} .
      - run: docker push myapp:${{ github.sha }}

Tools: GitHub Actions · Jenkins · GitLab CI · CircleCI

5.3 Kubernetes

# deployment.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: user-service
spec:
  replicas: 3
  selector:
    matchLabels:
      app: user-service
  template:
    spec:
      containers:
        - name: user-service
          image: user-service:latest
          ports: [{ containerPort: 8080 }]
          env:
            - name: DB_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: db-secret
                  key: password
          readinessProbe:
            httpGet:
              path: /actuator/health
              port: 8080

Key resources: Pods · Deployments · Services · ConfigMaps · Secrets · Ingress · HPA

5.4 Logging & Monitoring

ELK Stack: Logstash → Elasticsearch → Kibana

Structured logging:

logging:
  pattern:
    console: '{"time":"%d","level":"%p","traceId":"%X{traceId}","msg":"%m"}%n'

Recommended: Loki + Grafana (lighter alternative to ELK in 2026)

5.5 Caching & Performance

@EnableCaching
@SpringBootApplication
public class App { ... }

@Cacheable(value = "users", key = "#id")
public User getUser(Long id) { ... }

@CacheEvict(value = "users", key = "#user.id")
public User updateUser(User user) { ... }

Redis config:

spring:
  cache:
    type: redis
  data:
    redis:
      host: localhost
      port: 6379

Also learn: HikariCP connection pool tuning · @Async for non-blocking methods · Lazy loading vs Eager loading

5.6 Security Best Practices

HTTPS with TLS certificates (Let's Encrypt / cert-manager in K8s)
CSRF protection (for browser clients)
Rate limiting at Gateway level
Secure HTTP headers (X-Content-Type-Options, X-Frame-Options)
OAuth2 + Keycloak / Auth0 for identity management
Secrets management: HashiCorp Vault or K8s Secrets
OWASP Top 10 awareness

✅ After Phase 5: You can deploy and operate production systems.

Phase 6 – What's New & Often Missed (2026 Additions)

These topics were missing from the original roadmap but are critical in 2026.

6.1 Virtual Threads (Project Loom) – Java 21+

Spring Boot 3.2+ supports virtual threads out of the box, replacing traditional thread-per-request with lightweight virtual threads — massively improving throughput.

spring:
  threads:
    virtual:
      enabled: true

6.2 GraalVM Native Image

Compile Spring Boot apps to native executables for near-instant startup and low memory use — critical for serverless/Lambda deployments.

mvn -Pnative native:compile

Add spring-boot-starter-aot and configure @NativeHints for reflection-heavy code.

6.3 Spring WebFlux (Reactive Programming)

For high-concurrency, non-blocking APIs:

@GetMapping("/users/{id}")
public Mono<User> getUser(@PathVariable Long id) {
    return userRepository.findById(id);
}

@GetMapping("/users")
public Flux<User> getAllUsers() {
    return userRepository.findAll();
}

When to use: Real-time apps, streaming data, high I/O scenarios.

6.4 GraphQL with Spring Boot

@Controller
public class UserGraphQLController {

    @QueryMapping
    public User userById(@Argument Long id) {
        return userService.getUser(id);
    }

    @MutationMapping
    public User createUser(@Argument UserInput input) {
        return userService.create(input);
    }
}

Add spring-boot-starter-graphql — great for flexible client queries, BFF pattern.

6.5 Observability (Micrometer + OpenTelemetry)

Spring Boot 3.x ships with Micrometer Observation API. Prefer OpenTelemetry (OTel) over Sleuth for vendor-neutral tracing.

management:
  otlp:
    tracing:
      endpoint: http://otel-collector:4318/v1/traces

6.6 Database Migration (Flyway / Liquibase)

Never run raw DDL manually. Manage schema changes as versioned scripts:

-- db/migration/V1__create_users_table.sql
CREATE TABLE users (
    id BIGSERIAL PRIMARY KEY,
    email VARCHAR(255) UNIQUE NOT NULL,
    created_at TIMESTAMP DEFAULT NOW()
);

6.7 API Documentation (SpringDoc OpenAPI 3)

Replace Springfox (deprecated) with SpringDoc:

@Operation(summary = "Get user by ID")
@ApiResponse(responseCode = "200", description = "User found")
@GetMapping("/users/{id}")
public ResponseEntity<UserDTO> getUser(@PathVariable Long id) { ... }

Auto-generates Swagger UI at /swagger-ui.html.

6.8 Validation

public record CreateUserRequest(
    @NotBlank @Email String email,
    @NotBlank @Size(min = 8) String password,
    @NotNull @Min(18) Integer age
) {}

@PostMapping("/users")
public ResponseEntity<UserDTO> createUser(@Valid @RequestBody CreateUserRequest request) { ... }

6.9 MapStruct for DTO Mapping

@Mapper(componentModel = "spring")
public interface UserMapper {
    UserDTO toDTO(User user);
    User toEntity(CreateUserRequest request);
}

Avoids manual mapping errors; generates type-safe code at compile time.

6.10 gRPC with Spring Boot

For high-performance inter-service communication (alternative to REST):

@GrpcService
public class UserGrpcService extends UserServiceGrpc.UserServiceImplBase {
    @Override
    public void getUser(UserRequest request, StreamObserver<UserResponse> responseObserver) {
        // ...
    }
}

🏆 Final Project

Build: "Production-Ready E-Commerce Microservices System"

📦 e-commerce-platform/
├── 🔐 auth-service          (JWT + OAuth2 + Keycloak)
├── 👤 user-service           (CRUD + PostgreSQL + Flyway)
├── 📦 product-service        (CRUD + MongoDB)
├── 🛒 order-service          (Kafka Producer + Postgres)
├── 📊 inventory-service      (Kafka Consumer + Redis cache)
├── 🔔 notification-service   (Email/SMS on order events)
├── 🌐 api-gateway            (Spring Cloud Gateway + rate limiting)
├── 🗂️  config-server          (Git-backed configs)
├── 🔍 eureka-server          (Service discovery)
├── 📈 monitoring/            (Prometheus + Grafana + Loki)
└── 🐳 docker-compose.yml

Tech checklist:

[ ] JWT authentication & refresh tokens
[ ] API Gateway with rate limiting
[ ] Eureka service discovery
[ ] Config Server with Git backend
[ ] Circuit breaker (Resilience4j) on all Feign calls
[ ] Kafka event streaming (order → inventory → notification)
[ ] Dockerized with multi-stage builds
[ ] Kubernetes manifests (Deployments, Services, Ingress, HPA)
[ ] Prometheus + Grafana dashboards
[ ] ELK or Loki centralized logging
[ ] OpenAPI/Swagger documentation
[ ] Database migrations with Flyway
[ ] Distributed tracing with Zipkin/Jaeger

📅 Suggested Timeline

Phase	Duration	Focus
Phase 1 – Fundamentals	3–4 weeks	Core Spring Boot, CRUD, JPA
Phase 2 – Intermediate	3 weeks	Security, Testing, Monitoring
Phase 3 – Microservices Entry	2 weeks	Spring Cloud basics
Phase 4 – Resilience	3 weeks	Kafka, Resilience4j, Tracing
Phase 5 – DevOps	2–3 weeks	Docker, K8s, CI/CD
Phase 6 – 2026 Topics	Ongoing	Loom, Native, Reactive

Total: ~3–4 months of consistent learning (2–3 hours/day)

💡 Maximum ROI Focus: Security · Testing · Docker · Kubernetes · Distributed systems fundamentals — these separate average devs from high-paying backend engineers.

🔥 Top Interview Questions

Core Spring Boot

What is the difference between @Component, @Service, @Repository, and @Controller?

They're all @Component stereotypes. @Repository adds exception translation; @Service marks business logic; @Controller marks web layer. Use the most specific one for clarity and AOP.
How does Spring Boot auto-configuration work?

@EnableAutoConfiguration reads META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports, conditionally loading beans based on @ConditionalOnClass, @ConditionalOnMissingBean, etc.
What is the difference between @SpringBootApplication and @EnableAutoConfiguration?

@SpringBootApplication = @Configuration + @EnableAutoConfiguration + @ComponentScan. It's a convenience shortcut.
Explain application.properties vs application.yml. Which is preferred?

Both configure the app; YAML supports hierarchical structure and multiple documents. YAML is preferred for complex configs; properties for simple key-value.
What is a Spring Bean scope? Name all scopes.

Singleton (default), Prototype, Request, Session, Application, WebSocket.
What is the difference between @Autowired, @Inject, and @Resource?

@Autowired is Spring-specific (type-then-name). @Inject is JSR-330 (type-only). @Resource is JSR-250 (name-then-type). Constructor injection is preferred over field injection.

JPA & Database

What is the N+1 query problem and how do you solve it?

When fetching a list triggers N additional queries for associations. Solve with JOIN FETCH in JPQL, @EntityGraph, or @BatchSize.
What is the difference between EAGER and LAZY loading?

EAGER loads associations immediately; LAZY loads on access. LAZY is default for collections; EAGER can cause performance issues.
Explain @Transactional. What happens without it?

Without it, each repository call is its own transaction. @Transactional wraps a method in a single transaction, rolling back on RuntimeException by default.
What is the difference between save() and saveAndFlush() in JPA?

save() stages the operation; saveAndFlush() immediately synchronizes with the database within the current transaction.

Security

How does JWT authentication work in Spring Boot?

Client sends credentials → server validates and returns JWT → client sends JWT in Authorization: Bearer header → server validates token on each request via a OncePerRequestFilter.
What is the difference between authentication and authorization?

Authentication = who are you? Authorization = what can you do?
How do you prevent SQL injection in Spring Boot?

Use parameterized queries (JPA/JPQL does this by default). Avoid string concatenation in native queries.
What is CSRF and when should you disable it?

Cross-Site Request Forgery. Safe to disable for stateless REST APIs using JWT (no cookies). Keep it enabled for server-rendered apps with session cookies.

Microservices & Spring Cloud

What is the difference between Eureka and a load balancer?

Eureka = service registry (where are services?). Load balancer = how to distribute traffic. Spring Cloud LoadBalancer uses Eureka to find instances.
What is a circuit breaker? When does it open?

Prevents cascading failures. Opens when failure rate exceeds threshold (e.g., 50% in 10 calls), redirects to fallback for a wait duration, then tries half-open state.
Explain the difference between synchronous and asynchronous communication in microservices.

Synchronous (REST/gRPC): caller waits for response, tight coupling. Asynchronous (Kafka/RabbitMQ): fire-and-forget, loose coupling, better resilience.
What is Saga pattern?

Manages distributed transactions across microservices without 2PC. Choreography (events) or Orchestration (central coordinator) patterns.
How do you handle distributed transactions in microservices?

Use the Saga pattern with compensating transactions. Avoid distributed ACID transactions; prefer eventual consistency.
What is an API Gateway and why do you need it?

Single entry point for all clients. Handles cross-cutting concerns: auth, rate limiting, routing, SSL termination, logging — keeps individual services clean.

Testing

What is the difference between @Mock and @MockBean?

@Mock (Mockito): creates mock without Spring context. @MockBean: creates mock and registers it in Spring application context — use for integration tests.
What does @SpringBootTest load?

The full application context. Use @WebMvcTest for controller-only tests or @DataJpaTest for repository-only tests — they're faster.
How do you test a Kafka consumer in Spring Boot?

Use @EmbeddedKafka with @SpringBootTest to spin up an in-memory Kafka broker for integration tests.

Performance & DevOps

How do you optimize Spring Boot startup time?

Lazy initialization (spring.main.lazy-initialization=true), GraalVM native image, reduce component scan scope, use @Import over scanning.
What is HikariCP and why is it the default connection pool?

High-performance JDBC connection pool. Fastest available due to minimal bytecode and lock-free design. Spring Boot auto-configures it.
How do you monitor a Spring Boot application in production?

Spring Actuator exposes metrics → Prometheus scrapes them → Grafana visualizes → alerts on anomalies. Add distributed tracing via Micrometer + Zipkin/Jaeger.
What is the difference between horizontal and vertical scaling? Which does Spring Boot favor?

Vertical = bigger server. Horizontal = more instances. Spring Boot (especially with microservices) favors horizontal scaling — stateless design + Kubernetes HPA.
How do you implement zero-downtime deployments?

Rolling updates in Kubernetes, readiness probes to gate traffic, graceful shutdown with server.shutdown=graceful, database migration compatibility (expand-contract pattern).

Happy learning! Remember: build projects, not just tutorials. The best portfolio is working code. 🎯

carefree-ladka/🚀 Spring Boot Complete Roadmap (2026).mdx

🚀 Spring Boot Complete Roadmap (2026)

📋 Table of Contents

Phase 1 – Spring Boot Fundamentals

1.1 Introduction to Spring Boot

1.2 Creating a Spring Boot Project

1.3 REST Controller Basics

1.4 Database Integration – SQL

1.5 NoSQL Integration (Optional but Recommended)

1.6 Profiles & Environment Config

1.7 DevTools

1.8 Scheduling & Batch

Phase 2 – Intermediate (Professional API Developer Level)

2.1 Exception Handling

2.2 Spring Security

2.3 REST API Best Practices

2.4 Testing

2.5 Actuator & Monitoring

Phase 3 – Advanced Spring Boot (Microservices Entry)

3.1 Advanced Profiles

3.2 Spring Cloud Overview

3.3 Service Discovery (Eureka)

3.4 API Gateway

3.5 Centralized Config

Phase 4 – Microservices Communication & Resilience

4.1 Inter-Service Communication

4.2 Resilience4j

4.3 Distributed Tracing

4.4 Spring Cloud Bus

4.5 Event-Driven Architecture

Phase 5 – Deployment & DevOps

5.1 Docker

5.2 CI/CD

5.3 Kubernetes

5.4 Logging & Monitoring

5.5 Caching & Performance

5.6 Security Best Practices

Phase 6 – What's New & Often Missed (2026 Additions)

6.1 Virtual Threads (Project Loom) – Java 21+

6.2 GraalVM Native Image

6.3 Spring WebFlux (Reactive Programming)

6.4 GraphQL with Spring Boot

6.5 Observability (Micrometer + OpenTelemetry)

6.6 Database Migration (Flyway / Liquibase)

6.7 API Documentation (SpringDoc OpenAPI 3)

6.8 Validation

6.9 MapStruct for DTO Mapping

6.10 gRPC with Spring Boot

🏆 Final Project

📅 Suggested Timeline

🔥 Top Interview Questions

Core Spring Boot

JPA & Database

Security

Microservices & Spring Cloud

Testing

Performance & DevOps