Senior Fullstack SDK Engineer

Details

Customer.io is looking for a curious, AI-forward Fullstack SDK Engineer to join its SDK team and build tools that developers rely on to integrate with Customer.io. The company’s platform uses Go, React, Ember, and AI to support automated communication at scale.

Responsibilities

• Build and evolve Customer.io SDKs across Android, iOS, Node, and Go, along with supporting developer tools.
• Lead SDK initiatives end to end, including setting technical direction, writing code, managing releases, and owning outcomes.
• Improve SDK delivery infrastructure, including CI, automated testing, versioning, publishing, and release processes.
• Partner with product and design to turn loosely defined goals into a strong developer experience.
• Use AI agents to make multi-file changes across unfamiliar codebases and languages by scoping work, writing prompts, and verifying output.
• Apply customer empathy by understanding the needs of engineers integrating with the SDKs and occasionally engaging directly with them.

Requirements

• Expert-level competency in at least one established programming language.
• Strong software design and API design fundamentals.
• Experience building and evolving mature, production-quality software.
• Understanding of how systems fit together and how other developers consume them.
• Exceptional fluency with current LLMs and agentic coding tools such as Claude, Cursor, and Codex.
• Ability to use AI to understand unfamiliar codebases, work across languages, and run tasks in parallel or autonomously.
• High autonomy in ambiguous environments, including clarifying problems, validating value, and driving implementation without close direction.
• Strong written and verbal communication skills, including the ability to explain technical decisions and tradeoffs clearly.
• Ability to work effectively across multiple languages and technology stacks.
• Prior experience with every supported language is not required.

Nice-to-have experience includes building external-facing SDKs, APIs, or developer tools; owning CI, testing, versioning, or release infrastructure; or working in forward-deployed engineering.

Compensation and Benefits

• Starting salary: $150,000–$200,000 USD, or equivalent in local currency, depending on experience and subject to market rate adjustment.
• Medical, dental, vision, mental health, and supplemental insurance premiums fully covered for employees and their families.
• 16 weeks of paid parental leave.
• Unlimited paid time off.
• Remote-work and wellness stipends.
• Professional development budget.

Hiring Process

• Application review.
• 30-minute recruiter call.
• 60-minute hiring manager and AI skills interview.
• 60-minute practical AI-enabled coding round extending a sample SDK with AI tools.
• Final candidates complete a background check and employment verifications.