agents: Skill for Claude Code

Backend Developer

Expert in building production-grade backend APIs with the project's tech stack.

Layer References

Route→Service→Database architecture, tRPC router/service patterns, response format, and Zod schemas are covered in layers/project/typescript/service-layer.md and layers/project/typescript/architecture.md. This skill adds the step-by-step new-feature guide, middleware order, and BullMQ patterns not found in layers.

Creating a New Domain Feature

Step 1: Zod Schema (shared)

// packages/utils/src/validation/schemas.ts
export const createProductSchema = z.object({
  name: z.string().min(1),
  price: z.number().positive(),
  description: z.string().optional(),
});

Step 2: Service

// apps/api/src/services/product.service.ts
import { db } from "@repo/database";
import type { RequestContext } from "../context";

export const ProductService = {
  async create(input: CreateProductInput, ctx: RequestContext) {
    ctx.logger.info({ input }, "Creating product");
    return db.product.create({ data: input });
  },

  async getById(id: string, ctx: RequestContext) {
    const product = await db.product.findFirst({
      where: { id, deletedAt: null },
    });
    if (!product) throw new AppError("NOT_FOUND", t("errors.product_not_found"), 404);
    return product;
  },
};

Step 3: tRPC Router

// apps/api/src/routes/product.router.ts
import { router, protectedProcedure } from "../trpc";
import { createProductSchema } from "@repo/utils/validation";
import { ProductService } from "../services/product.service";

export const productRouter = router({
  create: protectedProcedure
    .input(createProductSchema)
    .mutation(({ input, ctx }) => ProductService.create(input, ctx)),

  getById: protectedProcedure
    .input(z.object({ id: z.string() }))
    .query(({ input, ctx }) => ProductService.getById(input.id, ctx)),
});

Step 4: Register Router

// apps/api/src/routes/index.ts
export const appRouter = router({
  auth: authRouter,
  user: userRouter,
  product: productRouter, // ← add here
});