Abridge Performance Tuning

Overview

Performance optimization for high-volume Abridge deployments. Large health systems process thousands of encounters daily — latency in note generation directly impacts clinical workflow throughput.

Performance Targets

Metric	Target	Critical Threshold
Audio stream → first transcript	< 2s	> 5s
Encounter → completed note	< 30s	> 60s
Note → EHR push	< 3s	> 10s
Patient summary generation	< 10s	> 30s
Concurrent sessions per org	100+	< 50

Prerequisites

• A staging or sandbox environment with synthetic encounter fixtures and a representative, authorized load profile.
• Baseline latency, error-rate, and concurrency measurements for the current release, with timestamps and measurement window recorded.
• Clinical, EHR, and security owners agree on safe concurrency limits and a rollback threshold before changing production traffic behavior.

Instructions

Step 1: Audio Streaming Optimization

// src/performance/audio-optimizer.ts
// Optimize audio chunk size and streaming for lowest latency

interface AudioStreamMetrics {
  chunkSize: number;
  sendInterval: number;
  bufferUtilization: number;
  latencyP50: number;
  latencyP99: number;
}

class OptimizedAudioStream {
  private buffer: Buffer[] = [];
  private metrics: AudioStreamMetrics = {
    chunkSize: 3200,       // 100ms at 16kHz 16-bit mono = 3200 bytes
    sendInterval: 100,     // Send every 100ms
    bufferUtilization: 0,
    latencyP50: 0,
    latencyP99: 0,
  };

  constructor(
    private ws: WebSocket,
    private sampleRate: number = 16000,
  ) {}

  // Optimal chunk size: 100ms for low latency, 500ms for bandwidth efficiency
  processAudioChunk(chunk: Buffer): void {
    this.buffer.push(chunk);

    const totalSize = this.buffer.reduce((sum, b) => sum + b.length, 0);
    if (totalSize >= this.metrics.chunkSize) {
      const combined = Buffer.concat(this.buffer);
      this.buffer = [];

      if (this.ws.readyState === WebSocket.OPEN) {
        const start = performance.now();
        this.ws.send(combined);
        this.recordLatency(performance.now() - start);
      }
    }
  }

  private recordLatency(ms: number): void {
    // Track P50/P99 for monitoring
    this.metrics.latencyP50 = ms; // Simplified — use histogram in production
  }

  getMetrics(): AudioStreamMetrics {
    return { ...this.metrics };
  }
}

Step 2: Note Generation Pipeline Optimization

// src/performance/note-pipeline.ts
// Pre-warm note generation and parallelize post-processing

interface PipelineStage {
  name: string;
  durationMs: number;
  parallel: boolean;
}

async function optimizedNotePipeline(
  api: any,
  sessionId: string,
): Promise<{ note: any; metrics: PipelineStage[] }> {
  const stages: PipelineStage[] = [];

  // Stage 1: Finalize session (triggers AI processing)
  const t1 = performance.now();
  await api.post(`/encounters/sessions/${sessionId}/finalize`);
  stages.push({ name: 'finalize', durationMs: performance.now() - t1, parallel: false });

  // Stage 2: Poll with exponential backoff (adaptive polling)
  const t2 = performance.now();
  let pollInterval = 500;  // Start fast
  let note = null;

  for (let i = 0; i < 30; i++) {
    const { data } = await api.get(`/encounters/sessions/${sessionId}/note`);
    if (data.status === 'completed') {
      note = data.note;
      break;
    }
    await new Promise(r => setTimeout(r, pollInterval));
    pollInterval = Math.min(pollInterval * 1.5, 3000); // Back off gradually
  }
  stages.push({ name: 'note_generation', durationMs: performance.now() - t2, parallel: false });

  if (!note) throw new Error('Note generation timed out');

  // Stage 3: Parallel post-processing
  const t3 = performance.now();
  const [patientSummary, ehrResult] = await Promise.allSettled([
    api.post(`/encounters/sessions/${sessionId}/patient-summary`, { language: 'en' }),
    pushNoteToEhr(note),
  ]);
  stages.push({ name: 'post_processing', durationMs: performance.now() - t3, parallel: true });

  return { note, metrics: stages };
}

Step 3: Connection Pooling for FHIR Push

// src/performance/connection-pool.ts
import axios from 'axios';
import https from 'https';

// Reuse TCP connections for FHIR endpoint
const fhirAgent = new https.Agent({
  keepAlive: true,
  keepAliveMsecs: 30000,
  maxSockets: 20,          // Max concurrent FHIR connections
  maxFreeSockets: 5,
  minVersion: 'TLSv1.3',
});

const fhirClient = axios.create({
  baseURL: process.env.EPIC_FHIR_BASE_URL,
  httpsAgent: fhirAgent,
  timeout: 10000,
});

// Batch FHIR pushes for multi-encounter processing
async function batchFhirPush(notes: Array<{ docRef: any }>): Promise<void> {
  // FHIR Bundle for batch operations
  const bundle = {
    resourceType: 'Bundle',
    type: 'batch',
    entry: notes.map(n => ({
      resource: n.docRef,
      request: { method: 'POST', url: 'DocumentReference' },
    })),
  };

  await fhirClient.post('/', bundle, {
    headers: { 'Content-Type': 'application/fhir+json' },
  });
}

Step 4: Performance Monitoring Dashboard

// src/performance/monitor.ts
interface PerformanceSnapshot {
  timestamp: string;
  activeSessions: number;
  avgNoteLatencyMs: number;
  p99NoteLatencyMs: number;
  fhirPushSuccessRate: number;
  audioStreamDropRate: number;
}

class PerformanceMonitor {
  private noteLatencies: number[] = [];
  private fhirPushResults: boolean[] = [];

  recordNoteLatency(ms: number): void {
    this.noteLatencies.push(ms);
    if (this.noteLatencies.length > 1000) this.noteLatencies.shift();
  }

  recordFhirPush(success: boolean): void {
    this.fhirPushResults.push(success);
    if (this.fhirPushResults.length > 1000) this.fhirPushResults.shift();
  }

  getSnapshot(activeSessions: number): PerformanceSnapshot {
    const sorted = [...this.noteLatencies].sort((a, b) => a - b);
    return {
      timestamp: new Date().toISOString(),
      activeSessions,
      avgNoteLatencyMs: sorted.length ? sorted.reduce((a, b) => a + b, 0) / sorted.length : 0,
      p99NoteLatencyMs: sorted.length ? sorted[Math.floor(sorted.length * 0.99)] : 0,
      fhirPushSuccessRate: this.fhirPushResults.length
        ? this.fhirPushResults.filter(Boolean).length / this.fhirPushResults.length
        : 1,
      audioStreamDropRate: 0, // Populated by audio stream metrics
    };
  }
}

Output

• Optimized audio streaming with 100ms chunking
• Adaptive polling for note generation (500ms → 3s backoff)
• Connection-pooled FHIR batch pushes
• Real-time performance monitoring with P50/P99 latency tracking

Examples

Run a staged load test using synthetic cardiology encounters at the approved concurrency level. Capture baseline and tuned P50/P99 note latency, FHIR push success rate, and audio-drop rate over the same measurement window. Enable connection pooling and adaptive polling only after the baseline is saved, then compare the two snapshots without logging transcripts or identifiers. If P99 latency, error rate, or downstream EHR saturation crosses the agreed threshold, disable the change and return traffic to the previous configuration before investigating the aggregate metrics.

Error Handling

Issue	Cause	Solution
High note latency	Complex encounter	Pre-segment long encounters
FHIR push timeout	EHR server overloaded	Use connection pool; batch pushes
Audio drops	Network jitter	Buffer 500ms; reconnect on drop

Resources

• Abridge Platform
• Node.js HTTPS Agent

Next Steps

For cost optimization, see abridge-cost-tuning.