API‑First: How Twilio Designs for Developers - Justin Kitagawa (Twilio)

How do you build an API so reliable it's used for suicide hotlines? Twilio's VP of Engineering explains their API-first design philosophy.

#1about 4 minutes

Understanding Twilio's role as a communications platform

Twilio provides the underlying communication infrastructure for SMS, email, and voice, focusing on high availability with SLOs of five and six nines.

#2about 3 minutes

Designing APIs for trust and backward compatibility

The API is the core product, built on trust and backward compatibility to support mission-critical systems and hardware-embedded clients without breaking changes.

#3about 3 minutes

Using composable primitives for flexible API design

A good developer API consists of composable "Lego block" primitives, like webhooks and TwiML verbs, that allow customers to build novel solutions.

#4about 4 minutes

Focusing on customer impact over feature requests

Instead of building a feature factory, the team uses the "five whys" technique to understand the root customer intent and prioritize work that delivers measurable impact.

#5about 3 minutes

Overcoming product silos caused by organizational structure

Conway's Law led to product silos after acquisitions, which was rectified by re-emphasizing a unified platform approach across all communication channels.

#6about 3 minutes

Revitalizing voice communication with AI for customer support

AI is driving a resurgence in voice usage by enabling intelligent routing and seamless handoffs between channels like voice, SMS, and chat for better customer experiences.

#7about 8 minutes

Engineering for operational excellence and high availability

Reliability is achieved through an operations-focused mindset, incremental deployments, assuming failure, and a cellular architecture to isolate impact.

#8about 3 minutes

Generating consistent SDKs and docs from OpenAPI specs

To solve fragmented and inconsistent SDKs, Twilio adopted a declarative approach using OpenAPI specs to automatically generate helper libraries and documentation.

#9about 5 minutes

Adapting the developer console for enterprise needs

The console evolved from a simple control panel for indie developers to a robust tool for enterprises, requiring features like RBAC and multi-organization support.

#10about 3 minutes

Why documentation is treated as a first-class product

High-quality documentation is crucial because it enables self-service for developers, reduces support tickets, and serves as the training data for AI models.

#11about 4 minutes

Addressing the security challenges of AI agents

A key challenge with AI is creating secure sandboxes and authorization systems to grant agents narrow, time-scoped permissions on a user's behalf.

#12about 5 minutes

Building trust with verified communication channels

To combat fraud and spoofing, Twilio is investing in trusted communication systems that verify a company's identity, ensuring calls and messages are legitimate.

#13about 3 minutes

Lessons from handling massive, unexpected traffic spikes

An early incident involving a celebrity taught valuable scaling lessons, leading to robust, modern DDoS protection strategies that rely on cloud partners and traffic filtering.