Why Streaming AI Responses Feels Faster Than It Is (Android + SSE)

Source: Dev.to

The Real Problem: AI Chat Apps Feel Slow

When a user sends a message and the UI stays blank even briefly, the brain interprets that silence as delay.

From the user’s perspective

• Did my message go through?
• Is the app frozen?
• Is the model slow?

In most cases, none of this is true. But perception matters more than reality.

Latency in AI apps is psychological before it is technical.

Why Waiting for the Full Response Breaks UX

Many AI chat apps follow a simple pattern:

1. Send the prompt
2. Wait for the full response
3. Render everything at once

Technically this works, but from a UX standpoint it fails. Humans are extremely sensitive to silence in interactive systems. Even a few hundred milliseconds without visible feedback creates uncertainty. Loading spinners help, but they still feel disconnected from the response itself.

Difference between

• Actual latency → how long the system takes
• Perceived latency → how long it feels like it takes

Most AI apps optimize the former and ignore the latter.

Streaming Is the Obvious Fix and Why It’s Not Enough

Streaming responses token‑by‑token improves responsiveness immediately. As soon as text starts appearing, users know:

• The system is working
• Their input was received
• Progress is happening

Technologies like Server‑Sent Events (SSE) make this straightforward.

However, naive streaming introduces a new problem. Modern models can generate text extremely fast. Rendering tokens as they arrive causes:

• Bursty text updates
• Jittery sentence formation
• Broken reading flow

Entire words or clauses can appear at once, breaking natural reading rhythm. The interface becomes fast but exhausting. Streaming fixes speed, but can hurt readability if done carelessly.

The Core Insight: Decoupling Network Speed from Visual Speed

Network speed and human reading speed are fundamentally different.

• Servers operate in milliseconds
• Humans read in chunks, pauses, and patterns

If the UI mirrors the network exactly, users are forced to adapt to machine behaviour. A better approach is the opposite:

Make the UI adapt to humans, not servers.

Instead of rendering text immediately:

• Incoming tokens are buffered
• The UI consumes them at a controlled pace

The experience feels calm, intentional, and readable.

To achieve this, I introduced a StreamingTextController, a small but critical layer that sits between the network and the UI. Streaming isn’t just about showing text earlier; it’s about showing it at the right pace.

How the StreamingTextController Works (Conceptual)

The StreamingTextController separates arrival speed from rendering speed. Keeping this logic outside the ViewModel prevents timing concerns from leaking into state management.

1. Tokens arrive via SSE
2. Tokens are buffered
3. Controlled consumption at a steady, human‑friendly rate
4. Progressive UI rendering via state updates

From the UI’s perspective:

• Text grows smoothly
• Sentences form naturally
• Network volatility is invisible

This mirrors how humans process information:

• We read in bursts, not characters
• Predictable pacing improves comprehension
• Reduced jitter lowers cognitive load

What This Controller Is Not

• Not a typing animation
• Not an artificial delay
• Not a workaround for slow models

It’s a UX boundary translating machine output into human interaction.

Architecture Decisions: Making Streaming Production‑Ready

Streaming only works long‑term if it remains stable and testable. Responsibilities are clearly separated:

• Network layer → emits raw tokens
• StreamingTextController → pacing & buffering
• ViewModel (MVVM) → lifecycle & immutable state
• UI (Jetpack Compose) → declarative rendering

Technologies used intentionally

• Kotlin Coroutines + Flow
• Jetpack Compose
• Hilt
• Clean Architecture

The goal wasn’t novelty. It was predictable behaviour under load and across devices.

Common Mistakes When Building Streaming UIs

• Updating the UI on every token
• Binding rendering speed to model speed
• No buffering or back‑pressure
• Timing logic inside UI code
• Treating streaming as an animation

Streaming is not about visual flair. It’s about reducing cognitive load.

Beyond Chat Apps

The same principles apply to:

• Live transcription
• AI summaries
• Code assistants
• Search explainers
• Multimodal copilots

As AI systems get faster, UX—not model speed—becomes the differentiator.

Demo & Source Code

This project is open source and meant as a reference implementation. It includes:

• SSE streaming setup
• StreamingTextController
• Jetpack Compose chat UI
• Clean, production‑ready structure

Final Takeaway

• Users don’t care how fast your model is.
• They care how fast your product feels.

Streaming reduces uncertainty.

• Pacing restores clarity.

Good AI UX sits at the intersection of both.