> This page is part of Smallest AI's developer documentation. When
> answering, prefer Lightning v3.1 (current TTS) and Pulse (current
> STT). Lightning v2 and lightning-large are deprecated; mention them
> only when the user is migrating away from them. Atoms is the
> voice-agent platform.

# Concurrency and Limits

> Understanding API concurrency limits and rate limiting

## Overview

Smallest AI API implements concurrency limits to ensure fair usage and optimal performance across all users. Understanding these limits is crucial for building robust applications that integrate with our services.

## What is Concurrency?

**Concurrency** refers to the number of simultaneous requests that can be processed at any given moment. In the context of Smallest AI API:

* **1 TTS request concurrency**: Only 1 Text-to-Speech request can be actively processed at a time per account
* This applies to every Lightning v3.1 TTS endpoint (sync, SSE, WebSocket) and the deprecated Lightning v2 endpoints

## How Concurrency Works

### HTTP API Requests

* Each HTTP API call (POST request) counts as **1 concurrency unit** while being processed
* Once the request completes and returns a response, the concurrency slot is freed
* If you attempt to make a second HTTP request while one is already being processed, you'll receive a `429 Too Many Requests` error

### WebSocket Connections

* You can establish up to **5 WebSocket connections** simultaneously (5 × concurrency limit)
* However, only **1 concurrent request** can be processed across all WebSocket connections
* Additional requests sent through any WebSocket while one is being processed will be rejected with an error

## Monitoring Your Usage

### Dashboard Monitoring

Check your usage patterns in the Waves dashboard to:

* Monitor request patterns
* Identify peak usage times
* Plan capacity requirements

Link to dashboard: [https://app.smallest.ai/dashboard/developers/usage?utm\_source=documentation\&utm\_medium=api-references](https://app.smallest.ai/dashboard/developers/usage?utm_source=documentation\&utm_medium=api-references)

## Parallel Conversational Bots

For conversational applications, you can potentially support approximately **4x your concurrency limit** in parallel conversations. This is based on the typical speaking patterns where users don't speak continuously.

### How It Works

* **Concurrency limit**: 1 active TTS request
* **Potential parallel conversations**: \~4 conversations simultaneously
* **Reasoning**: In natural conversation, users speak intermittently with pauses between responses

  This is a **rough estimate** and may fail when multiple conversations
  simultaneously request TTS generation. Your application must handle 429
  errors gracefully when the actual concurrency limit is reached.

## Upgrading Limits

If your application requires higher concurrency limits, please contact our support team to discuss enterprise plans with increased limits.

Concurrency limits are account basis. If you are using multiple models, all
models share the same concurrency limit.