Backend: Client vs. Server

Backend logic can run in the client or on the server. Knowing where to place functions is critical for security, scalability, and long-term maintainability.

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Table of contents

• What is client-side backend logic?
• What is server-side backend logic?
• Why developers start on the client
• Why moving to the server adds complexity
• The importance of proper backend separation
• How BaaS platforms simplify client vs. server decisions
• FAQs

What is client-side backend logic?

Client-side logic means application code (often written in JavaScript, Swift, or Kotlin) directly calls APIs, processes data, or even stores credentials.

Example

• A web app uploads an image and processes it in-browser with TensorFlow.js.
• A mobile app calls an S3 bucket directly using embedded credentials.

Pros

• Fast to prototype.
• Lower initial complexity.
• No backend infrastructure needed.

Cons

• Security risks (API keys exposed).
• Limited compute power (depends on user device).
• Hard to scale when usage grows.

What is server-side backend logic?

Server-side logic moves heavy lifting to centralized infrastructure (cloud or on-prem). The client sends requests, but the server handles secure processing, storage, and orchestration.

Example

• User uploads an image → serverless function runs inference → results stored in DB → client fetches predictions.

Pros

• Secure (no credentials exposed to the client).
• Scalable (run on powerful cloud resources).
• Centralized monitoring and logging.

Cons

• Higher setup complexity.
• Requires cloud infrastructure.
• Latency if not optimized.

Why developers start on the client

Early-stage apps often:

• Prototype directly in the browser or mobile app.
• Use client SDKs with hard-coded API calls.
• Skip infrastructure to save time.

This works until apps hit real-world needs: multi-user access, larger datasets, or compliance requirements.

Why moving to the server adds complexity

Shifting from client → server is rarely a copy-paste. It introduces:

• Authentication/authorization: verifying who’s calling your backend.
• Data flow orchestration: queues, retries, pipelines.
• Resource scaling: balancing cost vs. demand.
• Monitoring & logging: tracking usage, errors, performance.
• Separation of concerns: different teams managing frontend vs. backend.

The importance of proper backend separation

Well-structured backends:

• Protect sensitive data (no exposed keys).
• Centralize business logic (one source of truth).
• Enable scaling (add more compute, not more client devices).
• Simplify compliance (HIPAA, SOC2, GDPR).

How BaaS platforms simplify client vs. server decisions

With a platform like Lid Vizion, you don’t have to rebuild from scratch:

• Client code calls secure APIs instead of raw services.
• Serverless functions handle inference, search, and storage.
• Authentication and tenant separation are built in.
• Developers can start client-side for testing, then “flip” workloads server-side seamlessly.

This reduces the pain of migrating from quick prototypes to production-grade apps.

FAQs

Why can’t I just keep everything client-side?
It works for demos, but production apps need security, compliance, and scale — which require server-side logic.

Is moving logic server-side always slower?
Not if optimized. Serverless functions often run faster than client devices, especially for heavy AI tasks.

Can BaaS handle hybrid client + server?
Yes. Lightweight preprocessing can happen on the client; heavy lifting stays server-side.

What’s the biggest mistake teams make?
Embedding credentials or keys in client apps, which can be easily extracted.

Do I need a backend engineer to go server-side?
Not with BaaS. Platforms abstract away infrastructure so developers can focus on pipelines, not servers.

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