Agent skill
backend-patterns
Apply backend architecture patterns to the user's project. Covers repository pattern, service layer, middleware, error handling, validation, and database patterns. Adapts to the detected stack.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/other/backend-patterns-corbat-tech-coco
SKILL.md
Backend Patterns
Apply production-ready backend architecture patterns.
Stack Detection
Check for: package.json (Node/Express/Fastify/Hono), pom.xml (Spring Boot), pyproject.toml (FastAPI/Django), go.mod (Go/Gin/Fiber)
Universal Patterns (all stacks)
Repository Pattern
Separate data access from business logic:
// TypeScript
interface UserRepository {
findById(id: string): Promise<User | null>;
findAll(options: PaginationOptions): Promise<Page<User>>;
create(data: CreateUserDto): Promise<User>;
update(id: string, data: UpdateUserDto): Promise<User>;
delete(id: string): Promise<void>;
}
# Python
class UserRepository:
async def find_by_id(self, id: str) -> User | None: ...
async def find_all(self, options: PaginationOptions) -> Page[User]: ...
async def create(self, data: CreateUserDto) -> User: ...
Service Layer
Business logic lives in services, not controllers:
// TypeScript
class UserService {
constructor(private readonly userRepo: UserRepository) {}
async createUser(dto: CreateUserDto): Promise<User> {
// Business logic: validation, hashing, etc.
const existing = await this.userRepo.findByEmail(dto.email);
if (existing) throw new ConflictError("Email already exists");
const hashed = await bcrypt.hash(dto.password, 12);
return this.userRepo.create({ ...dto, password: hashed });
}
}
Error Handling Middleware
// TypeScript / Express
app.use((err: Error, req: Request, res: Response, next: NextFunction) => {
if (err instanceof ValidationError) {
return res.status(400).json({ error: { code: "VALIDATION_ERROR", message: err.message } });
}
if (err instanceof NotFoundError) {
return res.status(404).json({ error: { code: "NOT_FOUND", message: err.message } });
}
logger.error("Unhandled error", { error: err.message, stack: err.stack });
res.status(500).json({ error: { code: "INTERNAL_ERROR", message: "Internal server error" } });
});
Input Validation
// TypeScript with Zod
const CreateUserSchema = z.object({
email: z.string().email(),
password: z.string().min(8).max(72),
name: z.string().min(1).max(100),
});
// Python with Pydantic
class CreateUserDto(BaseModel):
email: EmailStr
password: str = Field(min_length=8, max_length=72)
name: str = Field(min_length=1, max_length=100)
N+1 Query Prevention
// ❌ N+1 problem
const users = await userRepo.findAll();
for (const user of users) {
user.posts = await postRepo.findByUserId(user.id); // N queries!
}
// ✅ Join or batch
const users = await userRepo.findAllWithPosts(); // 1 query with JOIN
// or use DataLoader pattern for GraphQL
Pagination Pattern
interface PaginationOptions {
page: number; // 1-based
limit: number; // max 100
}
interface Page<T> {
data: T[];
meta: { total: number; page: number; limit: number; totalPages: number };
}
Usage
/backend-patterns # review and improve current backend
/backend-patterns repository # add repository pattern
/backend-patterns service # add service layer
/backend-patterns error # add error handling
/backend-patterns validation # add input validation
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