Applied AI Engineer

The AI agent space is moving fast. Most companies are still figuring out what to build. We already know, and we need someone to help us build it.

Sendbird is on a mission to build the AI workforce of tomorrow. For over a decade, we built the infrastructure behind conversations—chat, voice, video, messaging APIs—and became the #1 CPaaS platform for in-app communications. 4,000+ brands trust us. 7 billion messages flow through our platform every month. 300 million monthly active users.

We powered conversations for DoorDash, Match Group, Noom, Yahoo Sports, Rakuten, and thousands of others. We were good at what we did. Really good.

We also saw it early: AI would fundamentally reshape how businesses talk to customers. The infrastructure we'd spent a decade building would become commoditized. The value would move up the stack—into intelligence, into experience, into outcomes.

We had a choice: protect what we built, or reinvent ourselves.

We chose reinvention.

In December 2024, we made the full strategic pivot to AI-first customer experience. By February 2025, we'd launched our AI agent for enterprise CX—built on a decade of conversation data, now with intelligence on top. And in November 2025, we rebranded to delight.ai.

The name says it all. AI's real promise isn't efficiency or cost savings. It's giving customers back something they lost—the feeling of being truly understood and cared for. Not satisfied. Delighted.

Delight.ai is the AI concierge for customer experience. Most AI agents forget you the moment the conversation ends. Ours doesn't. Delight.ai builds memory over time, learns preferences, and connects context across every channel—chat, SMS, email, voice, WhatsApp—without losing the thread. We're building AI that makes customers feel understood, seen, and remembered.

The next wave of AI isn't chatbots answering FAQs. It's agents that reason, remember, and act, proactively and accurately, at scale. That's what we're building, and we need someone who can build the backend brain behind it.

This is where research meets production. You'll take the latest advances in LLMs, RAG, and agentic systems and turn them into features that enterprise customers depend on every day. Not demos. Deployed, scaled, real. You'll also be expected to use AI tooling aggressively in your own workflow, automating pipelines, wiring together APIs, and building with agentic CLIs so your output compounds beyond what any single engineer could ship alone.

You'll design and build the core intelligence layer of our AI agents: retrieval systems, tool-calling pipelines, voice integrations, and agentic reasoning capabilities. You'll also be expected to use AI-native development tools and automation to accelerate your own work and the team around you. The right person thrives at the intersection of applied research, production engineering, and building with AI.

• You read AI research papers and your first instinct is to run an experiment, not write a summary.
• You've shipped LLM-powered features to production and you know exactly what separates a reliable system from a promising prototype.
• You obsess over latency, accuracy, and failure modes. "Kind of works" isn't in your vocabulary.
• You use agentic CLIs like Claude Code to move fast, and you wire APIs, automation platforms, or custom scripts together to eliminate repetitive work for yourself and your teammates.
• You get uncomfortable when prompt engineering is the only lever being pulled. You want to go deeper.
• You can evaluate a voice AI vendor on quality, cost, and real-world performance without needing a framework to tell you how.
• You communicate technical tradeoffs clearly enough that product managers and engineers can make real decisions.

• 5 or more years of professional experience in machine learning, data science, or applied AI engineering.
• Hands-on experience with AI agent frameworks such as LangChain or LlamaIndex, tool use, or advanced prompt engineering.
• Working knowledge of voice AI technologies, including Speech-to-Text and Text-to-Speech, with the ability to evaluate solutions across quality, latency, and cost.
• Fluency in Python with a track record of building and deploying production-grade services.

• Design and optimize the full backend pipeline for our AI agents, including advanced RAG systems, function-calling tools, and core agentic capabilities.
• Lead the integration and evaluation of voice AI solutions, third-party APIs, self-hosted models, and fine-tuned alternatives, with a hard focus on latency and quality.
• Prototype and implement new agent methodologies drawn from the latest LLM and agentic research, moving from experiment to production when results warrant it.
• Build and automate scalable Python services using agentic development tools, accelerating your output and reducing manual overhead across the full development lifecycle.
• Connect tools, APIs, and automation platforms to build internal pipelines that save time for the broader engineering team, not just yourself.
• Partner with product managers and engineers to translate complex requirements into shippable features without losing technical integrity.
• Embed AI agent capabilities directly into the Sendbird platform, ensuring the experience is coherent and powerful from the customer's point of view.

• Experience building natural language processing products.
• Familiarity with cloud platforms such as AWS, GCP, or Azure.
• Bilingual in Korean and English.

• Silicon Valley's equity program (1-year cliff) 
• Hybrid work policy, flexible work hours
• Be Your Best Self: 3.9 million won (prorated by start date) for expenses ranging from professional development classes and training, to personality assessments, to gym memberships, to books, to fitness classes, to mental health services, to massages
• Learn a Language benefit - up to 3.6 million won per year towards language lessons 
• Weekly team lunch cost
• Monthly team-building cost
• Partial support for commuting costs
• Free parking at the Seolleung office
• Group insurance support that covers employees, spouses, and children
• Medical checkup support, including MRI and genetic testing - for the employee and one family member
• Seven additional paid holidays in addition to annual leave (Boost leave, Birthday leave, etc.)
• Support for the latest work devices, such as MacBook Pro (special support options for each job position)
• Unlimited snack bar filled with snacks, beverages, and instant noodles every day
• 12-week paid parental leave support (available for both mothers and fathers)
• Other support programs for congratulations and condolences
  

We offer a flexible work schedule at Sendbird.  We also value collaboration and relationship building.  With those values in mind, we require all employees to gather with their team in the office three days per week as a minimum.  Some of our roles require a more frequent in-office schedule.  Please work with your manager to understand the office time requirements for your position.

There is no such thing as a perfect candidate and the best employees come from a wide range of backgrounds, experiences, and skill sets. Sendbird is a place where everyone can learn and grow. We respect, promote, and encourage diversity for equal employment opportunities and encourage you to apply if this role excites you.

Combining omnichannel AI and battle-tested, award-winning communication APIs, Sendbird enables businesses to build AI agents and meaningful customer connections at scale. Trusted by 4,000+ leading apps—including DoorDash, Match Group, Noom, and Yahoo Sports—Sendbird powers over 7 billion conversations every month, offering exceptional reliability, security, and compliance that meet enterprise-level demands. Headquartered in California, Sendbird is backed by ICONIQ, SoftBank, Tiger Global, Y Combinator, and other reputable investors.

We spent a decade building the conversation infrastructure that the world runs on. Now we're putting intelligence on top of it. You won't be joining a company still figuring out its AI strategy. You'll be joining one that has already made the bet, shipped the product, and is moving fast to lead the category. If you want to build something that matters, with a team that knows how, this is it.