API Gateway Designer

REST API Patterns

Resource-Oriented Endpoints

router.get('/api/users', requireAuth, async (req, res) => {
  const users = await userService.list(req.query);
  res.json({ data: users, meta: { total: users.length } });
});

router.post('/api/users', requireAuth, async (req, res) => {
  const user = await userService.create(req.body);
  res.status(201).json({ data: user });
});

router.get('/api/users/:id', requireAuth, async (req, res) => {
  const user = await userService.getById(req.params.id);
  if (!user) throw new NotFoundError('User not found');
  res.json({ data: user });
});

Query Builder with Pagination

class QueryBuilder<T> {
  build() {
    let q = db.select().from(this.table);
    if (this.query.filter) {
      q = q.where(and(...conditions));
    }
    q = q.limit(this.query.limit).offset((this.query.page - 1) * this.query.limit);
    return q;
  }
}

GraphQL Schema

builder.prismaObject('User', {
  fields: (t) => ({
    id: t.exposeID('id'),
    email: t.exposeString('email'),
    posts: t.relation('posts'),
  })
});

builder.queryType({
  fields: (t) => ({
    user: t.prismaField({
      type: 'User',
      args: { id: t.arg.id({ required: true }) },
      resolve: (query, _, args) => db.user.findUnique({ ...query, where: { id: args.id } })
    })
  })
});

WebSocket Handler

export class WebSocketManager {
  broadcast(channel: string, payload: unknown) {
    this.clients.forEach(client => {
      if (client.subscriptions.has(channel)) {
        client.send(JSON.stringify({ channel, payload }));
      }
    });
  }
}

Middleware

export const rateLimitMiddleware = async (req, res, next) => {
  try {
    await rateLimiter.consume(req.user?.id || req.ip);
    next();
  } catch {
    res.status(429).json({ error: 'Too many requests' });
  }
};

Protocol

1. Assess — Understand the specific requirement and context
2. Plan — Determine the approach based on the guidance above
3. Execute — Apply the api gateway designer methodology
4. Verify — Validate the output against expected standards
5. Report — Document results and any issues encountered