861b28b965
New skills (14): - nestjs-best-practices: 40 priority-ranked rules (kadajett) - fastapi: Pydantic v2, async SQLAlchemy, JWT auth (jezweb) - architecture-patterns: Clean Architecture, Hexagonal, DDD (wshobson) - python-performance-optimization: Profiling and optimization (wshobson) - ai-sdk: Vercel AI SDK streaming and agent patterns (vercel) - create-agent: Modular agent architecture with OpenRouter (openrouterteam) - proactive-agent: WAL Protocol, compaction recovery, self-improvement (halthelobster) - brand-guidelines: Brand identity enforcement (anthropics) - ui-animation: Motion design with accessibility (mblode) - marketing-ideas: 139 ideas across 14 categories (coreyhaines31) - pricing-strategy: SaaS pricing and tier design (coreyhaines31) - programmatic-seo: SEO at scale with playbooks (coreyhaines31) - competitor-alternatives: Comparison page architecture (coreyhaines31) - referral-program: Referral and affiliate programs (coreyhaines31) README reorganized by domain: Code Quality, Frontend, Backend, Auth, AI/Agent Building, Marketing, Design, Meta. Mosaic Stack is not limited to coding — the Orchestrator serves coding, business, design, marketing, writing, logistics, and analysis. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
3.2 KiB
3.2 KiB
title, impact, impactDescription, tags
| title | impact | impactDescription | tags |
|---|---|---|---|
| Optimize Database Queries | HIGH | Database queries are typically the largest source of latency | performance, database, queries, optimization |
Optimize Database Queries
Select only needed columns, use proper indexes, avoid over-fetching relations, and consider query performance when designing your data access. Most API slowness traces back to inefficient database queries.
Incorrect (over-fetching data and missing indexes):
// Select everything when you need few fields
@Injectable()
export class UsersService {
async findAllEmails(): Promise<string[]> {
const users = await this.repo.find();
// Fetches ALL columns for ALL users
return users.map((u) => u.email);
}
async getUserSummary(id: string): Promise<UserSummary> {
const user = await this.repo.findOne({
where: { id },
relations: ['posts', 'posts.comments', 'posts.comments.author', 'followers'],
});
// Over-fetches massive relation tree
return { name: user.name, postCount: user.posts.length };
}
}
// No indexes on frequently queried columns
@Entity()
export class Order {
@Column()
userId: string; // No index - full table scan on every lookup
@Column()
status: string; // No index - slow status filtering
}
Correct (select only needed data with proper indexes):
// Select only needed columns
@Injectable()
export class UsersService {
async findAllEmails(): Promise<string[]> {
const users = await this.repo.find({
select: ['email'], // Only fetch email column
});
return users.map((u) => u.email);
}
// Use QueryBuilder for complex selections
async getUserSummary(id: string): Promise<UserSummary> {
return this.repo
.createQueryBuilder('user')
.select('user.name', 'name')
.addSelect('COUNT(post.id)', 'postCount')
.leftJoin('user.posts', 'post')
.where('user.id = :id', { id })
.groupBy('user.id')
.getRawOne();
}
// Fetch relations only when needed
async getFullProfile(id: string): Promise<User> {
return this.repo.findOne({
where: { id },
relations: ['posts'], // Only immediate relation
select: {
id: true,
name: true,
email: true,
posts: {
id: true,
title: true,
},
},
});
}
}
// Add indexes on frequently queried columns
@Entity()
@Index(['userId'])
@Index(['status'])
@Index(['createdAt'])
@Index(['userId', 'status']) // Composite index for common query pattern
export class Order {
@PrimaryGeneratedColumn('uuid')
id: string;
@Column()
userId: string;
@Column()
status: string;
@CreateDateColumn()
createdAt: Date;
}
// Always paginate large datasets
@Injectable()
export class OrdersService {
async findAll(page = 1, limit = 20): Promise<PaginatedResult<Order>> {
const [items, total] = await this.repo.findAndCount({
skip: (page - 1) * limit,
take: limit,
order: { createdAt: 'DESC' },
});
return {
items,
meta: {
page,
limit,
total,
totalPages: Math.ceil(total / limit),
},
};
}
}
Reference: TypeORM Query Builder