Streamlining Legacy Databases: A Lead QA Engineer's TypeScript Approach to Cluttered Production Systems

#typescript #database #legacy

Managing legacy codebases often presents unique challenges, particularly when it comes to maintaining clean and efficient production databases. As a Lead QA Engineer, I faced a recurring issue: databases cluttered with redundant, inconsistent, and poorly structured data — a situation that hampers performance, complicates troubleshooting, and increases risk during deployments.

To address this, I employed TypeScript to craft targeted scripts and tools that gradually refactor and optimize our database structures, even within a legacy environment. This approach allowed me to leverage TypeScript's strong typing, modern syntax, and ease of integration with existing CI/CD pipelines.

Understanding the Challenge

Legacy systems often contain a mix of tables and data models that evolved over years without strict standardization. Common problems include:

Duplicate records across multiple tables
Inconsistent data formats
Orphaned records and broken foreign key references
Unused or obsolete data segments

These issues create “clutter” that impacts query performance, data integrity, and overall system robustness.

Strategy for Clutter Reduction

My strategy centered on incremental cleanup, data deduplication, and schema normalization, achieved through TypeScript-based scripts that performed the following:

Data profiling to identify redundancies and inconsistencies
Automated deduplication to remove duplicates
Referential integrity checks to uncover orphaned entries
Schema adjustments to normalize data structure

This process involved writing scripts that could be safely run in production, with careful logging and rollback capabilities.

Implementing the Solution in TypeScript

Here's a simplified example illustrating how I used TypeScript for deduplicating user records based on an email address:

import { Client } from 'pg';

const client = new Client({
  connectionString: process.env.DATABASE_URL,
});

async function deduplicateUsers() {
  await client.connect();
  try {
    const duplicates = await client.query(`
      SELECT email, array_agg(id ORDER BY id) AS ids
      FROM users
      GROUP BY email
      HAVING COUNT(id) > 1;
    `);

    for (const row of duplicates.rows) {
      const ids = row.ids;
      // Keep the first ID, delete others
      const [keepId, ...deleteIds] = ids;

      // Delete duplicates
      await client.query(`
        DELETE FROM users WHERE id = ANY($1)
      `, [deleteIds]);

      console.log(`Deduplicated email: ${row.email}, kept ID: ${keepId}`);
    }
  } catch (error) {
    console.error('Error during deduplication', error);
  } finally {
    await client.end();
  }
}

deduplicateUsers();

This script uses modern TypeScript features while maintaining compatibility with a PostgreSQL database. It performs safe deduplication while providing logs for traceability.

Benefits and Lessons Learned

Implementing TypeScript scripts for database cleanup enabled several advantages:

Type safety caught potential bugs early in development
Reusable and easy-to-maintain code
Seamless integration into existing processes
Improved confidence through scripting of repeatable cleanups

While working on legacy codebases, I found that adopting a typed language like TypeScript helps bridge the gap between old and new, providing a controlled environment to implement systematic improvements. The key is crafting scripts that are idempotent, safe, and comprehensively logged.

Final Thoughts

Transforming cluttered production databases in legacy systems is fundamentally about implementing a disciplined, incremental approach. TypeScript acts as both a development and a validation layer, helping engineers ensure data integrity and system performance improvements without risking downtime or data loss.

By breaking down large, complex cleanup tasks into targeted scripts, QA teams can lead operational improvements that extend the lifespan and reliability of legacy systems, ultimately delivering better service and stability to users.