Southeast Asia Voice OTP & Notification Solution

Client Background

Industry: Financial Technology

A fintech company operating across multiple Southeast Asian countries needed voice OTP (one-time password) and voice notification services for user registration, transaction verification, and security alerts. This scenario demanded extremely high delivery speed and delivery rates, with support for high-concurrency call volumes.

Challenges Before Deployment

The company relied on SMS-based OTP for user verification, but SMS delivery in several Southeast Asian markets was unreliable, with high latency and significant message filtering by local carriers. Voice OTP was needed as a complementary and fallback verification channel.

Key pain points included:

• Unreliable SMS delivery: SMS OTP messages in several markets suffered from high filtering rates and variable delivery times, undermining user verification workflows.
• High concurrency demands: Flash registration events and promotional campaigns generated sudden spikes in OTP requests that overwhelmed existing infrastructure.
• Speed requirements: Financial verification use cases required OTP delivery within seconds, making any PDD or call setup delay unacceptable.
• Multi-country complexity: Each Southeast Asian market had different carrier requirements, numbering regulations, and route quality characteristics.

Solution

Cainiao Voice provisioned a high-concurrency dedicated SIP trunk with TTS (text-to-speech) system integration and premium routes optimized for each Southeast Asian country. Routing strategies were tailored to OTP traffic patterns, ensuring minimal PDD (post-dial delay) and rapid delivery.

The solution included:

• High-concurrency SIP trunk capable of sustaining 500+ simultaneous calls to handle peak OTP demand.
• TTS integration for dynamic voice OTP content generation, supporting multiple languages across Southeast Asian markets.
• Premium route optimization with per-country routing strategies tuned for short-duration, high-volume OTP traffic patterns.
• Minimal PDD configuration through direct-carrier and near-carrier routes, targeting sub-100ms call setup times.
• Real-time delivery monitoring with per-call tracking of delivery rate, PDD, and completion status.

Technical Architecture

Key Metrics

Measurement Scope

PDD = delay from SIP INVITE to 180 Ringing, median value; delivery time = total elapsed time from API call to endpoint ring; delivery rate = successful ring attempts / API calls x 100%, measured over 30 consecutive operating days.

Client Feedback

"OTP delivery is fast and the user experience is excellent. Lines remain stable even under high concurrency, with delivery rates consistently above 99%, meeting the stringent requirements of our financial business for security verification."