Backend Project Architecture Design

🎯 Core Question

From simple scripts to large distributed systems, how do you choose the right architecture for backend projects of different scales and languages? It's like asking: from a home workshop to a large factory, how do you design different production lines based on output and processes? Good backend architecture should evolve with business growth while fully leveraging language characteristics.

1. Architecture Evolution: From Script to System

1.1 Architecture Levels by User Count

Backend project architecture should match business scale and user volume:

Level	Users	Concurrency	Typical Scenario	Key Focus
Entry	< 1k	< 100	Personal projects, MVP, internal tools	Rapid development, simple deployment
Intermediate	1k-100k	100-10k	Enterprise systems, SaaS, mid-size platforms	Layered architecture, coding standards
Enterprise	> 100k	> 10k	Large platforms, internet applications	Microservices, high availability, performance optimization

1.2 Choosing Architectural Style by Language Characteristics

Different programming languages have different design philosophies and ecosystems — architecture design should align with language characteristics:

Language	Design Philosophy	Recommended Architecture	Representative Frameworks
Node.js	Event-driven, non-blocking I/O	Layered architecture + async flows	Express, NestJS, Fastify
Python	Simple and elegant, rapid development	MTV/MVC, layered architecture	Django, Flask, FastAPI
Go	Simple and efficient, native concurrency	Clean layering, microservices	Gin, Echo, Fiber
Java	Enterprise-grade, strong typing	Strict layering, domain-driven	Spring Boot, Spring Cloud

💡 Architecture Selection Principles

Don't over-engineer: Small projects use simple architectures; large projects need complex architectures
Follow language characteristics: Don't try to write Java-style code in Python
Progressive evolution: Start simple, optimize gradually as the business grows
Team familiarity: Choose architecture styles your team is familiar with to reduce learning costs

2. Entry-Level Architecture (Users < 1k)

2.1 Applicable Scenarios

Personal projects, learning exercises
Startup MVP (Minimum Viable Product)
Internal tools, admin dashboards
Prototype validation, proof of concept

2.2 Node.js — Simple Scripting Style

Characteristics: Single file or simple split, quick to launch

my-node-api/
├── src/
│   ├── app.js              # Application entry point
│   ├── routes.js           # Route definitions
│   ├── db.js               # Database connection
│   └── utils.js            # Utility functions
├── .env                    # Environment variables
├── package.json
└── README.md

Code Example:

javascript

// src/app.js
const express = require('express');
const app = express();

app.use(express.json());

// Routes written directly in the entry point (suitable when there are very few endpoints)
app.get('/users', async (req, res) => {
  const users = await db.query('SELECT * FROM users');
  res.json(users);
});

app.post('/users', async (req, res) => {
  const { name, email } = req.body;
  const result = await db.query(
    'INSERT INTO users (name, email) VALUES (?, ?)',
    [name, email]
  );
  res.status(201).json({ id: result.insertId });
});

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

Reference Open Source Projects:

expressjs/express — Official examples
vercel/micro — Microservice style

2.3 Python — Rapid Prototyping Style

Characteristics: Leverage Python's simplicity for fast feature implementation

my-python-api/
├── app.py                  # Main application
├── models.py               # Data models
├── config.py               # Configuration
├── requirements.txt
└── README.md

Code Example (Flask):

python

# app.py
from flask import Flask, request, jsonify
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
db = SQLAlchemy(app)

# Model definitions
class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(80), nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)

# Routes
@app.route('/users', methods=['GET'])
def get_users():
    users = User.query.all()
    return jsonify([{'id': u.id, 'name': u.name, 'email': u.email} for u in users])

@app.route('/users', methods=['POST'])
def create_user():
    data = request.json
    user = User(name=data['name'], email=data['email'])
    db.session.add(user)
    db.session.commit()
    return jsonify({'id': user.id}), 201

if __name__ == '__main__':
    app.run(debug=True)

Reference Open Source Projects:

pallets/flask — Official examples
tiangolo/fastapi — Modern async style

2.4 Go — Clean Standard Library Style

Characteristics: Leverage Go's standard library with minimal dependencies

my-go-api/
├── main.go                 # Entry point
├── handlers.go             # Handlers
├── models.go               # Models
├── db.go                   # Database
├── go.mod
└── README.md

Code Example:

// main.go
package main

import (
    "database/sql"
    "encoding/json"
    "log"
    "net/http"
    _ "github.com/mattn/go-sqlite3"
)

type User struct {
    ID    int    `json:"id"`
    Name  string `json:"name"`
    Email string `json:"email"`
}

var db *sql.DB

func main() {
    var err error
    db, err = sql.Open("sqlite3", "./app.db")
    if err != nil {
        log.Fatal(err)
    }

    http.HandleFunc("/users", usersHandler)
    log.Println("Server starting on :8080")
    log.Fatal(http.ListenAndServe(":8080", nil))
}

func usersHandler(w http.ResponseWriter, r *http.Request) {
    switch r.Method {
    case http.MethodGet:
        getUsers(w, r)
    case http.MethodPost:
        createUser(w, r)
    }
}

func getUsers(w http.ResponseWriter, r *http.Request) {
    rows, _ := db.Query("SELECT id, name, email FROM users")
    defer rows.Close()

    var users []User
    for rows.Next() {
        var u User
        rows.Scan(&u.ID, &u.Name, &u.Email)
        users = append(users, u)
    }

    json.NewEncoder(w).Encode(users)
}

Reference Open Source Projects:

golang/go — Standard library examples
go-chi/chi — Lightweight router

2.5 Java — Spring Boot Starter Style

Characteristics: Leverage Spring Boot's auto-configuration for quick startup

my-spring-app/
├── src/main/java/com/example/
│   ├── controller/
│   │   └── UserController.java
│   ├── model/
│   │   └── User.java
│   ├── repository/
│   │   └── UserRepository.java
│   └── Application.java
├── src/main/resources/
│   └── application.yml
├── pom.xml
└── README.md

Code Example:

java

// Application.java
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

// User.java
@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String email;
    // getters and setters
}

// UserRepository.java
public interface UserRepository extends JpaRepository<User, Long> {
}

// UserController.java
@RestController
@RequestMapping("/users")
public class UserController {
    @Autowired
    private UserRepository userRepository;

    @GetMapping
    public List<User> getAllUsers() {
        return userRepository.findAll();
    }

    @PostMapping
    public User createUser(@RequestBody User user) {
        return userRepository.save(user);
    }
}

Reference Open Source Projects:

spring-projects/spring-boot — Official examples
spring-projects/spring-petclinic — Classic example

3. Intermediate Architecture (Users 1k–100k)

3.1 Applicable Scenarios

Enterprise management systems (ERP, CRM, OA)
SaaS applications
E-commerce platforms
Projects requiring multi-team collaboration

3.2 Layered Architecture Explained

Intermediate projects are recommended to adopt a four-layer architecture (Controller-Service-Repository-Model):

project/
├── src/
│   ├── controllers/          # Controller layer: handles HTTP requests
│   ├── services/             # Service layer: business logic
│   ├── repositories/         # Repository layer: data access
│   ├── models/               # Model layer: data structures
│   ├── middlewares/          # Middleware
│   ├── utils/                # Utility functions
│   ├── config/               # Configuration
│   └── routes/               # Route definitions
├── tests/
├── docs/
└── scripts/

3.3 Node.js — Enterprise Layered

Reference Open Source Projects:

nestjs/nest — Enterprise Node.js framework
goldbergyoni/nodebestpractices — Node.js best practices

node-enterprise/
├── src/
│   ├── modules/              # Organized by feature modules
│   │   ├── users/
│   │   │   ├── users.controller.ts
│   │   │   ├── users.service.ts
│   │   │   ├── users.repository.ts
│   │   │   ├── users.module.ts
│   │   │   └── dto/
│   │   ├── orders/
│   │   └── products/
│   ├── common/               # Shared modules
│   │   ├── filters/          # Exception filters
│   │   ├── guards/           # Guards
│   │   ├── interceptors/     # Interceptors
│   │   └── pipes/            # Pipes
│   ├── config/
│   └── main.ts

NestJS Code Example:

typescript

// users/users.controller.ts
@Controller('users')
export class UsersController {
  constructor(private readonly usersService: UsersService) {}

  @Get()
  findAll(@Query() query: QueryUserDto) {
    return this.usersService.findAll(query);
  }

  @Post()
  create(@Body() createUserDto: CreateUserDto) {
    return this.usersService.create(createUserDto);
  }
}

// users/users.service.ts
@Injectable()
export class UsersService {
  constructor(
    @InjectRepository(User)
    private usersRepository: Repository<User>,
  ) {}

  async findAll(query: QueryUserDto) {
    const [data, total] = await this.usersRepository.findAndCount({
      skip: (query.page - 1) * query.limit,
      take: query.limit,
    });
    return { data, total };
  }

  async create(createUserDto: CreateUserDto) {
    const user = this.usersRepository.create(createUserDto);
    return this.usersRepository.save(user);
  }
}

3.4 Python — Django/DRF Style

Reference Open Source Projects:

django/django — Official project
encode/django-rest-framework — REST framework
cookiecutter/cookiecutter-django — Project template

django-enterprise/
├── apps/
│   ├── users/                # Users app
│   │   ├── models.py
│   │   ├── views.py          # API views
│   │   ├── serializers.py    # Serializers
│   │   ├── permissions.py    # Permissions
│   │   ├── urls.py
│   │   └── tests/
│   ├── orders/
│   └── products/
├── config/                   # Project configuration
│   ├── settings/
│   │   ├── base.py
│   │   ├── development.py
│   │   └── production.py
│   ├── urls.py
│   └── wsgi.py
├── utils/                    # Shared utilities
├── templates/
├── static/
└── manage.py

Django REST Framework Code Example:

python

# users/models.py
from django.contrib.auth.models import AbstractUser

class User(AbstractUser):
    phone = models.CharField(max_length=20, blank=True)
    avatar = models.URLField(blank=True)

# users/serializers.py
from rest_framework import serializers

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ['id', 'username', 'email', 'phone', 'avatar']

# users/views.py
from rest_framework import viewsets, permissions
from rest_framework.decorators import action

class UserViewSet(viewsets.ModelViewSet):
    queryset = User.objects.all()
    serializer_class = UserSerializer
    permission_classes = [permissions.IsAuthenticated]

    @action(detail=False, methods=['get'])
    def me(self, request):
        serializer = self.get_serializer(request.user)
        return Response(serializer.data)

# users/urls.py
from rest_framework.routers import DefaultRouter

router = DefaultRouter()
router.register(r'users', UserViewSet)

urlpatterns = router.urls

3.5 Go — Clean Architecture Style

Reference Open Source Projects:

gin-gonic/gin — Web framework
go-kit/kit — Microservices toolkit
bxcodec/go-clean-arch — Clean architecture example

go-enterprise/
├── cmd/
│   └── api/                  # Application entry point
│       └── main.go
├── internal/                 # Private code
│   ├── domain/               # Domain layer (entities, interfaces)
│   │   ├── user.go
│   │   └── repository.go
│   ├── usecase/              # Use case layer (business logic)
│   │   └── user_usecase.go
│   ├── delivery/             # Delivery layer (HTTP/gRPC)
│   │   └── http/
│   │       └── user_handler.go
│   ├── repository/           # Repository layer (data access)
│   │   └── user_repository.go
│   └── config/
├── pkg/                      # Public libraries
├── migrations/
└── go.mod

Clean Architecture Code Example:

// domain/user.go
type User struct {
    ID        int64     `json:"id"`
    Username  string    `json:"username"`
    Email     string    `json:"email"`
    CreatedAt time.Time `json:"created_at"`
}

// domain/repository.go
type UserRepository interface {
    GetByID(ctx context.Context, id int64) (*User, error)
    GetByEmail(ctx context.Context, email string) (*User, error)
    Create(ctx context.Context, user *User) error
    Update(ctx context.Context, user *User) error
}

// usecase/user_usecase.go
type UserUsecase struct {
    userRepo UserRepository
}

func (u *UserUsecase) GetByID(ctx context.Context, id int64) (*User, error) {
    return u.userRepo.GetByID(ctx, id)
}

func (u *UserUsecase) Create(ctx context.Context, user *User) error {
    // Business logic: check if email already exists
    existing, _ := u.userRepo.GetByEmail(ctx, user.Email)
    if existing != nil {
        return errors.New("email already exists")
    }
    return u.userRepo.Create(ctx, user)
}

// delivery/http/user_handler.go
type UserHandler struct {
    UserUsecase *usecase.UserUsecase
}

func (h *UserHandler) GetUser(c *gin.Context) {
    id, _ := strconv.ParseInt(c.Param("id"), 10, 64)
    user, err := h.UserUsecase.GetByID(c.Request.Context(), id)
    if err != nil {
        c.JSON(404, gin.H{"error": "user not found"})
        return
    }
    c.JSON(200, user)
}

3.6 Java — Spring Boot Enterprise

Reference Open Source Projects:

spring-projects/spring-boot
spring-cloud-samples — Microservice examples
ali-baba/spring-cloud-alibaba — Alibaba microservices

spring-enterprise/
├── src/main/java/com/example/
│   ├── application/          # Application layer
│   │   ├── controller/       # Controllers
│   │   ├── dto/              # Data transfer objects
│   │   └── assembler/        # Assemblers
│   ├── domain/               # Domain layer
│   │   ├── entity/           # Entities
│   │   ├── valueobject/      # Value objects
│   │   ├── repository/       # Repository interfaces
│   │   └── service/          # Domain services
│   ├── infrastructure/       # Infrastructure layer
│   │   ├── repository/       # Repository implementations
│   │   ├── config/           # Configuration
│   │   └── common/           # Utility classes
│   └── Application.java
├── src/main/resources/
│   ├── application.yml
│   └── mapper/
└── src/test/

Domain-Driven Design (DDD) Code Example:

java

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

    @Column(nullable = false)
    private String username;

    @Column(nullable = false, unique = true)
    private String email;

    @Embedded
    private UserStatus status;

    // Domain methods
    public void deactivate() {
        this.status = UserStatus.INACTIVE;
    }

    public boolean isActive() {
        return this.status == UserStatus.ACTIVE;
    }
}

// domain/repository/UserRepository.java
public interface UserRepository {
    Optional<User> findById(Long id);
    Optional<User> findByEmail(String email);
    User save(User user);
    void delete(User user);
}

// application/controller/UserController.java
@RestController
@RequestMapping("/api/v1/users")
@RequiredArgsConstructor
public class UserController {
    private final UserService userService;
    private final UserAssembler userAssembler;

    @GetMapping("/{id}")
    public ResponseEntity<UserDTO> getUser(@PathVariable Long id) {
        User user = userService.findById(id);
        return ResponseEntity.ok(userAssembler.toDTO(user));
    }

    @PostMapping
    public ResponseEntity<UserDTO> createUser(@RequestBody @Valid CreateUserRequest request) {
        User user = userService.createUser(request);
        return ResponseEntity.status(HttpStatus.CREATED)
                .body(userAssembler.toDTO(user));
    }
}

// infrastructure/repository/UserRepositoryImpl.java
@Repository
@RequiredArgsConstructor
public class UserRepositoryImpl implements UserRepository {
    private final UserJpaRepository jpaRepository;

    @Override
    public Optional<User> findById(Long id) {
        return jpaRepository.findById(id);
    }

    @Override
    public User save(User user) {
        return jpaRepository.save(user);
    }
}

4. Enterprise Architecture (Users > 100k)

4.1 Applicable Scenarios

Large internet platforms
Financial trading systems
High-concurrency e-commerce systems
Large projects requiring multi-team collaboration

4.2 Microservices Architecture

When a monolithic application can no longer meet requirements, consider a microservices architecture:

microservices-platform/
├── api-gateway/              # API Gateway
│   ├── src/
│   └── Dockerfile
├── services/                 # Business services
│   ├── user-service/         # User service
│   ├── order-service/        # Order service
│   ├── product-service/      # Product service
│   └── payment-service/      # Payment service
├── shared/                   # Shared libraries
│   ├── proto/                # Protocol Buffers
│   ├── common-lib/
│   └── event-contracts/
├── infrastructure/           # Infrastructure
│   ├── docker-compose.yml
│   ├── kubernetes/
│   └── terraform/
└── docs/

4.3 Microservices Frameworks by Language

Language	Microservices Framework	Service Discovery	Config Center	Distributed Tracing
Node.js	NestJS + gRPC	Consul	etcd	Jaeger
Python	FastAPI + Nameko	Eureka	Consul	Zipkin
Go	Go-kit + gRPC	etcd	etcd	OpenTelemetry
Java	Spring Cloud	Nacos	Nacos	SkyWalking

4.4 Codebase Design (Monorepo vs Polyrepo)

Monorepo (Single Repository):

monorepo/
├── services/
│   ├── user-service/         # Independent service
│   │   ├── src/
│   │   ├── package.json
│   │   └── Dockerfile
│   ├── order-service/
│   └── product-service/
├── shared/
│   ├── types/                # Shared types
│   ├── utils/                # Shared utilities
│   └── proto/                # Shared protocols
├── packages/
│   ├── eslint-config/        # Shared ESLint config
│   └── ts-config/            # Shared TS config
├── docker-compose.yml
└── package.json              # Root package.json

Advantages:

Easy code sharing
Unified build and release
Easy refactoring

Disadvantages:

Large codebase
Complex permission management

Polyrepo (Multiple Repositories):

Each service has its own repository:

github.com/company/user-service
github.com/company/order-service
github.com/company/shared-lib

Advantages:

Services evolve independently
Team autonomy
Clear permissions

Disadvantages:

Difficult code sharing
Complex version management

4.5 Data Layer Design

Database Selection Strategy:

Data Type	Recommended Database	Use Case
Relational data	PostgreSQL	Users, orders, products
Cache	Redis	Sessions, hot data
Search	Elasticsearch	Product search, logs
Time-series data	InfluxDB/TimescaleDB	Monitoring, metrics
Document data	MongoDB	Logs, configuration

Data Access Layer Design:

data-layer/
├── primary-db/               # Primary database
│   ├── master/               # Write database
│   └── slaves/               # Read replicas
├── cache-layer/              # Cache layer
│   ├── redis-cluster/
│   └── local-cache/
├── search-engine/            # Search engine
│   └── elasticsearch/
└── message-queue/            # Message queue
    ├── kafka/
    └── rabbitmq/

5. Open Source Project Architecture References

5.1 Node.js Ecosystem

Express.js Official Project Structure:

express-project/
├── bin/                      # Startup scripts
├── public/                   # Static assets
├── routes/                   # Routes
├── views/                    # Views
├── app.js                    # Application configuration
└── package.json

NestJS Official Recommendation:

nest-project/
├── src/
│   ├── modules/              # Feature modules
│   ├── common/               # Shared modules
│   ├── config/
│   └── main.ts
├── test/
└── nest-cli.json

5.2 Python Ecosystem

Django Official Project Structure:

django-project/
├── project_name/             # Project configuration
├── apps/                     # Apps directory
├── templates/
├── static/
├── media/
└── manage.py

FastAPI Project Structure:

fastapi-project/
├── app/
│   ├── api/
│   │   ├── deps.py           # Dependencies
│   │   └── v1/
│   │       └── endpoints/
│   ├── core/                 # Core configuration
│   ├── db/                   # Database
│   ├── models/               # Models
│   ├── schemas/              # Pydantic models
│   └── main.py
├── tests/
└── alembic/                  # Migrations

5.3 Go Ecosystem

Standard Project Layout:

go-project/
├── cmd/                      # Application entry points
│   └── app/
│       └── main.go
├── internal/                 # Private code
├── pkg/                      # Public libraries
├── api/                      # API definitions
├── web/                      # Static assets
├── configs/                  # Configuration
├── scripts/                  # Scripts
└── go.mod

Reference:

golang-standards/project-layout

5.4 Java Ecosystem

Spring Boot Official Structure:

spring-boot-project/
├── src/main/java/com/example/
│   ├── controller/
│   ├── service/
│   ├── repository/
│   ├── entity/
│   ├── dto/
│   ├── config/
│   └── Application.java
├── src/main/resources/
│   ├── static/
│   ├── templates/
│   └── application.yml
└── src/test/

Alibaba Java Development Manual:

Clear layering: controller/service/manager/dao
Domain models: distinguish DO/DTO/BO/VO
Package structure: organized by feature modules

6. Architecture Evolution Roadmap

6.1 Evolution Example

Phase 1: Monolithic Application (Entry Level)
    ↓ User growth, team expansion
Phase 2: Layered Architecture (Intermediate Level)
    ↓ Business complexity, multi-team collaboration
Phase 3: Modular/Microservices (Enterprise Level)
    ↓ High concurrency, high availability requirements
Phase 4: Cloud-Native Architecture (Platform Level)

6.2 When to Upgrade Architecture?

Signal	Current Level	Recommended Upgrade
Code files > 50	Entry	Intermediate
Build time > 5 minutes	Intermediate	Modular
Team > 10 people	Intermediate	Microservices
DAU > 100k	Intermediate	Enterprise
Multi-language tech stack	Monolith	Microservices

7. Summary

💡 Core Ideas

Architecture serves the business, not architecture for architecture's sake.

Choose by user count:

< 1k: Simple scripts, quick to launch
1k–100k: Layered architecture, coding standards
> 100k: Microservices, high-availability design

Choose by language:

Node.js: Leverage async characteristics, suitable for I/O-intensive workloads
Python: Rapid development, suitable for data processing and AI
Go: High performance, suitable for cloud-native and microservices
Java: Enterprise-grade, suitable for large complex systems

Universal principles:

Progressive evolution: Start simple, grow with the business
Convention over configuration: Unified standards reduce communication costs
Automated testing: Ensure safe refactoring
Documentation first: Record architectural decisions

The ultimate goal: Make your code run as efficiently as a factory floor, regardless of scale.

Reference Resources

Open Source Projects

nestjs/nest — Node.js enterprise framework
django/django — Python web framework
gin-gonic/gin — Go web framework
spring-projects/spring-boot — Java framework

Architecture Guides

goldbergyoni/nodebestpractices — Node.js best practices
golang-standards/project-layout — Go project layout
cookiecutter/cookiecutter-django — Django project template
ali-baba/spring-cloud-alibaba — Alibaba microservices

Books

Clean Architecture — Robert C. Martin
Building Microservices — Sam Newman
Designing Data-Intensive Applications — Martin Kleppmann

Backend Project Architecture Design ​

1. Architecture Evolution: From Script to System ​

1.1 Architecture Levels by User Count ​

1.2 Choosing Architectural Style by Language Characteristics ​

2. Entry-Level Architecture (Users < 1k) ​

2.1 Applicable Scenarios ​

2.2 Node.js — Simple Scripting Style ​

2.3 Python — Rapid Prototyping Style ​

2.4 Go — Clean Standard Library Style ​

2.5 Java — Spring Boot Starter Style ​

3. Intermediate Architecture (Users 1k–100k) ​

3.1 Applicable Scenarios ​

3.2 Layered Architecture Explained ​

3.3 Node.js — Enterprise Layered ​

3.4 Python — Django/DRF Style ​

3.5 Go — Clean Architecture Style ​

3.6 Java — Spring Boot Enterprise ​

4. Enterprise Architecture (Users > 100k) ​

4.1 Applicable Scenarios ​

4.2 Microservices Architecture ​

4.3 Microservices Frameworks by Language ​

4.4 Codebase Design (Monorepo vs Polyrepo) ​

4.5 Data Layer Design ​

5. Open Source Project Architecture References ​

5.1 Node.js Ecosystem ​

5.2 Python Ecosystem ​

5.3 Go Ecosystem ​

5.4 Java Ecosystem ​

6. Architecture Evolution Roadmap ​

6.1 Evolution Example ​

6.2 When to Upgrade Architecture? ​

7. Summary ​

Reference Resources ​

Open Source Projects ​

Architecture Guides ​

Books ​

Backend Project Architecture Design

1. Architecture Evolution: From Script to System

1.1 Architecture Levels by User Count

1.2 Choosing Architectural Style by Language Characteristics

2. Entry-Level Architecture (Users < 1k)

2.1 Applicable Scenarios

2.2 Node.js — Simple Scripting Style

2.3 Python — Rapid Prototyping Style

2.4 Go — Clean Standard Library Style

2.5 Java — Spring Boot Starter Style

3. Intermediate Architecture (Users 1k–100k)

3.1 Applicable Scenarios

3.2 Layered Architecture Explained

3.3 Node.js — Enterprise Layered

3.4 Python — Django/DRF Style

3.5 Go — Clean Architecture Style

3.6 Java — Spring Boot Enterprise

4. Enterprise Architecture (Users > 100k)

4.1 Applicable Scenarios

4.2 Microservices Architecture

4.3 Microservices Frameworks by Language

4.4 Codebase Design (Monorepo vs Polyrepo)

4.5 Data Layer Design

5. Open Source Project Architecture References

5.1 Node.js Ecosystem

5.2 Python Ecosystem

5.3 Go Ecosystem

5.4 Java Ecosystem

6. Architecture Evolution Roadmap

6.1 Evolution Example

6.2 When to Upgrade Architecture?

7. Summary

Reference Resources

Open Source Projects

Architecture Guides

Books