Concurrency

Synthflow enforces concurrency and rate limits to maintain system stability and call quality. This page explains the limits by tier and how they apply to your account.

Concurrency limits by tier

• Starter: 10 concurrent calls
• Pro: 25 concurrent calls
• Growth: 50 concurrent calls
• Agency: 100 concurrent calls
• Enterprise: 100+ concurrent calls (with priority queuing)

Rate limits

There is a cap on call attempts per second. By default, accounts can attempt one outbound call per second (3,600 per hour). This limit applies to all tiers.

Behavior when limits are exceeded

• Non‑Enterprise tiers: Exceeding the concurrency or rate limit returns a 429 HTTP error. Excess calls are not processed.
• Enterprise tier: A priority queueing system processes calls exceeding the limit with a brief delay, providing flexibility and scalability.

Scope

These limits apply to outbound calls only. Inbound calls are not affected.

If you use workflows with GoHighLevel, HubSpot, Zapier, or other automation tools, implement a delay or throttle mechanism when batching calls to stay within limits.

Custom limits

Enterprise customers can request custom concurrency or rate limits. Contact our sales team to discuss your requirements.