Why We Built a Local-First Data Generator (Privacy & Speed)

The Problem with Traditional Mock Data Generators

When we started building MockBlast, we asked developers what frustrated them about existing mock data tools. The answers were surprising:

🔓 Privacy Concerns

"I can't use [popular tool] at work because it sends our database schema to their servers. Our security team won't approve it."

🐌 Slow Performance

"Every time I make a small change to my schema, I have to wait for the tool to re-sync with their servers. It breaks my flow."

📡 Network Dependencies

"I work on trains and planes. When I don't have internet, I can't even edit my schemas, let alone generate data."

The Local-First Solution

We designed MockBlast around three core principles:

🔒 Privacy by Default

Your schema is your intellectual property. We parse CREATE TABLE statements locally in your browser using WebAssembly. Your table names, column names, and business logic never touch our servers. Only the final generated data (which doesn't reveal your schema) is streamed back.

⚡ Instant Feedback

No network round-trips for schema parsing means instant validation. See errors immediately, preview your schema structure instantly, and iterate fast. The only network call is for data generation, which happens server-side for maximum performance.

💻 Offline-Capable

Build and edit schemas without internet. While you need connectivity for data generation, all schema work happens locally. This respects your workflow and keeps you productive anywhere.

How It Works: The Architecture

1. Local Schema Parsing

// Pseudo-code: Local schema parsing
1. Parse SQL in browser (client-side)
2. Extract schema structure
3. Validate syntax
4. No network call needed
5. Schema never leaves device

2. Data Generation Request

// Pseudo-code: Minimal server request
Send to server:
  - Row count
  - Field types needed
  - Data generation preferences

NOT sent:
  - Table names
  - Column names
  - Business logic
  - Schema structure

3. Server-Side Generation

// Pseudo-code: Server generates data
1. Receive minimal request
2. Generate rows based on field types
3. Stream data back to client
4. No schema knowledge required
5. Fast, scalable generation

Real-World Benefits

🏢 Enterprise Compliance

Because schemas never leave the browser:

• Passes most security audits
• No data sovereignty concerns
• No DPA/GDPR issues
• Works behind corporate firewalls

⚡ Developer Experience

Instant feedback loop:

• Zero-latency schema validation
• Immediate error messages
• Preview schema without generating
• No "syncing..." spinners

🚀 Performance

Hybrid approach wins:

• Local parsing: instant
• Server generation: scalable
• Streaming: no waiting
• Best of both worlds

🔐 Security

Reduced attack surface:

• No schema in server logs
• No schema in database
• Can't leak what we don't have
• Minimal data transmission

What We Learned Building Local-First

Challenge 1: SQL Parsing in the Browser

Parsing SQL is complex. We evaluated using WebAssembly ports of server-side parsers, but they were too large (5MB+ downloads). Instead, we built a lightweight parser in TypeScript that handles the 90% case of common CREATE TABLE syntax. It's fast, small (50KB), and works offline.

Challenge 2: Balancing Local vs. Remote

We experimented with fully local generation using Web Workers, but generating millions of rows in the browser was slow and crashed tabs. The hybrid approach—local parsing, remote generation—gives us privacy without sacrificing performance.

Challenge 3: State Management

Local-first means state lives in the browser. We use IndexedDB for persistence and React Query for state synchronization. Your schemas auto-save locally and sync to our servers (encrypted) only if you choose to save them for later.

The Future of Local-First

We believe local-first is the future for developer tools. Here's what's next:

•Fully Offline Generation: WebAssembly-based faker library for complete offline operation.
•Peer-to-Peer Collaboration: Share schemas with your team without our servers using WebRTC.
•End-to-End Encryption: If you choose to save schemas to our cloud, they'll be E2E encrypted. We can't read them.
•CLI Tool: Generate data completely locally using our CLI tool. No network required.

Try MockBlast Today

Experience the difference of local-first data generation:

1.Paste your CREATE TABLE statement—it never leaves your browser
2.See instant validation and schema preview
3.Generate data with one click—fast and private
4.Download SQL INSERT statements or JSON

Start Generating Data →