Speak Performance Tuning

---
name: speak-performance-tuning
description: |
  Optimize Speak API performance with caching, audio preprocessing, and connection pooling.
  Use when experiencing slow API responses, implementing caching strategies,
  or optimizing request throughput for language learning applications.
  Trigger with phrases like "speak performance", "optimize speak",
  "speak latency", "speak caching", "speak slow", "speak audio optimization".
allowed-tools: Read, Write, Edit
version: 1.0.0
license: MIT
author: Jeremy Longshore <jeremy@intentsolutions.io>
---

# Speak Performance Tuning

## Overview
Optimize Speak API performance with caching, audio preprocessing, and connection pooling for language learning applications.

## Prerequisites
- Speak SDK installed
- Understanding of async patterns
- Redis or in-memory cache available (optional)
- Performance monitoring in place

## Latency Benchmarks

| Operation | P50 | P95 | P99 |
|-----------|-----|-----|-----|
| Session Start | 200ms | 500ms | 1000ms |
| Tutor Prompt | 150ms | 300ms | 600ms |
| Text Response Submit | 100ms | 250ms | 500ms |
| Audio Recognition | 500ms | 1500ms | 3000ms |
| Pronunciation Scoring | 800ms | 2000ms | 4000ms |

## Audio Optimization

### Pre-processing Audio Before Upload
```typescript
class AudioOptimizer {
  // Optimize audio for Speak's speech recognition
  async optimizeForRecognition(audioData: ArrayBuffer): Promise<ArrayBuffer> {
    // Convert to optimal format: 16kHz mono PCM WAV
    const audioContext = new AudioContext({ sampleRate: 16000 });
    const audioBuffer = await audioContext.decodeAudioData(audioData);

    // Convert to mono if stereo
    const monoBuffer = this.toMono(audioBuffer);

    // Normalize audio levels
    const normalizedBuffer = this.normalize(monoBuffer);

    // Remove silence at start/end
    const trimmedBuffer = this.trimSilence(normalizedBuffer);

    // Encode as WAV
    return this.encodeWav(trimmedBuffer);
  }

  private toMono(buffer: AudioBuffer): AudioBuffer {
    if (buffer.numberOfChannels === 1) return buffer;

    const monoData = new Float32Array(buffer.length);
    const left = buffer.getChannelData(0);
    const right = buffer.getChannelData(1);

    for (let i = 0; i < buffer.length; i++) {
      monoData[i] = (left[i] + right[i]) / 2;
    }

    const ctx = new OfflineAudioContext(1, buffer.length, buffer.sampleRate);
    const newBuffer = ctx.createBuffer(1, buffer.length, buffer.sampleRate);
    newBuffer.copyToChannel(monoData, 0);
    return newBuffer;
  }

  private normalize(buffer: AudioBuffer): AudioBuffer {
    const data = buffer.getChannelData(0);
    let max = 0;

    for (let i = 0; i < data.length; i++) {
      max = Math.max(max, Math.abs(data[i]));
    }

    if (max > 0 && max < 0.9) {
      const factor = 0.9 / max;
      for (let i = 0; i < data.length; i++) {
        data[i] *= factor;
      }
    }

    return buffer;
  }

  private trimSilence(buffer: AudioBuffer, threshold = 0.01): AudioBuffer {
    const data = buffer.getChannelData(0);
    let start = 0;
    let end = data.length;

    // Find start
    for (let i = 0; i < data.length; i++) {
      if (Math.abs(data[i]) > threshold) {
        start = Math.max(0, i - 1000); // Keep small buffer
        break;
      }
    }

    // Find end
    for (let i = data.length - 1; i >= 0; i--) {
      if (Math.abs(data[i]) > threshold) {
        end = Math.min(data.length, i + 1000);
        break;
      }
    }

    const trimmedLength = end - start;
    const ctx = new OfflineAudioContext(1, trimmedLength, buffer.sampleRate);
    const newBuffer = ctx.createBuffer(1, trimmedLength, buffer.sampleRate);
    newBuffer.copyToChannel(data.slice(start, end), 0);
    return newBuffer;
  }
}
```

### Streaming Audio for Real-time Recognition
```typescript
class StreamingRecognizer {
  private chunks: ArrayBuffer[] = [];
  private processingPromise: Promise<void> | null = null;

  async streamAudioChunk(chunk: ArrayBuffer): Promise<PartialResult | null> {
    this.chunks.push(chunk);

    // Process in batches to reduce API calls
    if (this.chunks.length >= 5 || this.shouldProcess()) {
      return this.processAccumulated();
    }

    return null;
  }

  private async processAccumulated(): Promise<PartialResult> {
    const combinedSize = this.chunks.reduce((sum, c) => sum + c.byteLength, 0);
    const combined = new ArrayBuffer(combinedSize);
    const view = new Uint8Array(combined);

    let offset = 0;
    for (const chunk of this.chunks) {
      view.set(new Uint8Array(chunk), offset);
      offset += chunk.byteLength;
    }

    this.chunks = [];

    const result = await speakClient.speech.recognizeStream(combined);
    return result;
  }
}
```

## Caching Strategy

### Response Caching for Static Content
```typescript
import { LRUCache } from 'lru-cache';

// Cache tutor prompts and audio URLs
const promptCache = new LRUCache<string, TutorPrompt>({
  max: 500,
  ttl: 60 * 60 * 1000, // 1 hour
  updateAgeOnGet: true,
});

// Cache vocabulary lookups
const vocabularyCache = new LRUCache<string, VocabularyEntry>({
  max: 10000,
  ttl: 24 * 60 * 60 * 1000, // 24 hours
});

async function getCachedVocabulary(
  word: string,
  language: string
): Promise<VocabularyEntry> {
  const key = `${language}:${word}`;
  const cached = vocabularyCache.get(key);
  if (cached) return cached;

  const entry = await speakClient.vocabulary.lookup(word, language);
  vocabularyCache.set(key, entry);
  return entry;
}
```

### Redis Caching for Distributed Systems
```typescript
import Redis from 'ioredis';

const redis = new Redis(process.env.REDIS_URL);

async function cachedWithRedis<T>(
  key: string,
  fetcher: () => Promise<T>,
  ttlSeconds = 3600
): Promise<T> {
  const cached = await redis.get(key);
  if (cached) {
    return JSON.parse(cached);
  }

  const result = await fetcher();
  await redis.setex(key, ttlSeconds, JSON.stringify(result));
  return result;
}

// Cache user progress
async function getUserProgress(userId: string): Promise<UserProgress> {
  return cachedWithRedis(
    `speak:progress:${userId}`,
    () => speakClient.users.getProgress(userId),
    300 // 5 minutes
  );
}
```

### Audio Asset Caching
```typescript
// Pre-fetch and cache audio assets
class AudioAssetCache {
  private cache: Map<string, ArrayBuffer> = new Map();
  private preloadQueue: Set<string> = new Set();

  async preloadLessonAudio(lessonId: string): Promise<void> {
    const lesson = await speakClient.lessons.get(lessonId);

    // Pre-fetch all audio for the lesson
    const audioUrls = lesson.items.map(item => item.audioUrl);

    await Promise.all(
      audioUrls.map(async (url) => {
        if (!this.cache.has(url) && !this.preloadQueue.has(url)) {
          this.preloadQueue.add(url);
          const response = await fetch(url);
          const buffer = await response.arrayBuffer();
          this.cache.set(url, buffer);
          this.preloadQueue.delete(url);
        }
      })
    );
  }

  async getAudio(url: string): Promise<ArrayBuffer> {
    const cached = this.cache.get(url);
    if (cached) return cached;

    const response = await fetch(url);
    const buffer = await response.arrayBuffer();
    this.cache.set(url, buffer);
    return buffer;
  }
}
```

## Connection Optimization

```typescript
import { Agent } from 'https';

// Keep-alive connection pooling
const agent = new Agent({
  keepAlive: true,
  maxSockets: 10,
  maxFreeSockets: 5,
  timeout: 60000,
});

const client = new SpeakClient({
  apiKey: process.env.SPEAK_API_KEY!,
  appId: process.env.SPEAK_APP_ID!,
  httpAgent: agent,
  timeout: 30000,
});
```

## Request Batching

```typescript
import DataLoader from 'dataloader';

// Batch vocabulary lookups
const vocabularyLoader = new DataLoader<string, VocabularyEntry>(
  async (words) => {
    // Batch API call
    const results = await speakClient.vocabulary.batchLookup(words);
    return words.map(word => results.find(r => r.word === word) || null);
  },
  {
    maxBatchSize: 50,
    batchScheduleFn: callback => setTimeout(callback, 50),
  }
);

// Usage - automatically batched
const [word1, word2, word3] = await Promise.all([
  vocabularyLoader.load('hola'),
  vocabularyLoader.load('buenos'),
  vocabularyLoader.load('días'),
]);
```

## Performance Monitoring

```typescript
interface SpeakMetrics {
  operation: string;
  duration: number;
  success: boolean;
  audioSize?: number;
}

async function measuredSpeakCall<T>(
  operation: string,
  fn: () => Promise<T>,
  metadata?: Record<string, any>
): Promise<T> {
  const start = performance.now();
  try {
    const result = await fn();
    const duration = performance.now() - start;

    // Log metrics
    console.log({
      operation,
      duration,
      success: true,
      ...metadata,
    });

    // Track in metrics system
    metrics.histogram('speak_api_duration', duration, { operation });
    metrics.increment('speak_api_success', { operation });

    return result;
  } catch (error) {
    const duration = performance.now() - start;

    console.error({
      operation,
      duration,
      success: false,
      error,
      ...metadata,
    });

    metrics.histogram('speak_api_duration', duration, { operation });
    metrics.increment('speak_api_error', { operation });

    throw error;
  }
}

// Usage
const result = await measuredSpeakCall(
  'speech.recognize',
  () => speakClient.speech.recognize(audioBuffer),
  { audioSize: audioBuffer.byteLength }
);
```

## Output
- Reduced API latency
- Audio preprocessing pipeline
- Caching layer implemented
- Request batching enabled
- Connection pooling configured

## Error Handling
| Issue | Cause | Solution |
|-------|-------|----------|
| Cache miss storm | TTL expired | Use stale-while-revalidate |
| Audio too large | No compression | Optimize audio format |
| Connection exhausted | No pooling | Configure max sockets |
| Memory pressure | Cache too large | Set max cache entries |
| Batch timeout | Too many items | Reduce batch size |

## Examples

### Quick Performance Wrapper
```typescript
const withPerformance = <T>(name: string, fn: () => Promise<T>) =>
  measuredSpeakCall(name, () =>
    cachedWithRedis(`cache:${name}`, fn, 300)
  );
```

## Resources
- [Speak Performance Guide](https://developer.speak.com/docs/performance)
- [Web Audio API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API)
- [DataLoader Documentation](https://github.com/graphql/dataloader)
- [LRU Cache Documentation](https://github.com/isaacs/node-lru-cache)

## Next Steps
For cost optimization, see `speak-cost-tuning`.