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Senior Fastapi Developer Jobs in Boston, MA (NOW HIRING)

Klaviyo

Senior AI Application Engineer

Boston, MA

We are looking for a Senior IT App Engineer to design, build, and scale production-grade LLM ... Strong full-stack engineering skills across Python (FastAPI, Flask, or Django) and TypeScript or ...

Klaviyo

Sr. Manager, Orchestrate

Boston, MA

$137.40K - $181.40K/yr

As the Senior Engineering Manager for Orchestrate, you will lead multiple teams responsible for the ... Django/FastAPI or similar) * Experience with cloud infrastructure (AWS), DevOps practices, and ...

CVS Health

Senior Data Engineer

Wellesley, MA · On-site

$92.70K - $222.48K/yr

Develop Python-based APIs (Flask/FastAPI) to enable seamless data access, model integration, and ... Knowledge of CI/CD and DevOps practices for data engineering * Experience with other cloud services ...

BitSight

Senior Software Engineer I

Boston, MA · On-site +1

$133.50K - $175.90K/yr

As a Senior Software Engineer, you will be expected to think on your feet, learn quickly, and take ... Experience with modern Python frameworks and technologies, such as Django, FastAPI, Flask ...

Klaviyo

Senior AI Engineer

Boston, MA · On-site

$133.10K - $175.50K/yr

Senior Software Engineer - Marketing Agent Location: Boston, MA (Hybrid 3x week) At Klaviyo, we ... Proficient in Python and modern web stack components such as FastAPI, Django, MySQL, Postgres.

Conga

Senior Software Engineer

Boston, MA · On-site

$133.10K - $175.50K/yr

You have: * Experience in Python and frameworks such as TensorFlow, PyTorch, FastAPI, LangChain ... Proficiency with cloud platforms (e.g., GCP, AWS, Azure) and modern DevOps practices. * Strong ...

Klaviyo

Senior AI Engineer

Boston, MA

$133.10K - $175.50K/yr

Senior Software Engineer - Marketing Agent Location: Boston, MA (Hybrid 3x week) At Klaviyo, we ... Proficient in Python and modern web stack components such as FastAPI, Django, MySQL, Postgres.

Farsyt

Founding Senior Software Engineer

Cambridge, MA · On-site

$133.90K - $176.50K/yr

Strong backend engineering skills -- you've built and scaled real systems (we use Python, but care ... Technical Stack Python (Django/DRF, FastAPI), React/TypeScript, PostgreSQL, Redis, Celery, AWS ...

Klaviyo

Senior AI Application Engineer

Boston, MA

We are looking for a Senior AI Engineer to design, build, and scale production-grade LLM ... Strong full-stack engineering skills across Python (FastAPI, Flask, or Django) and TypeScript or ...

VIA

Senior Software Engineer

Somerville, MA · On-site

$133.70K - $176.20K/yr

An impressive mission requires an equally impressive Senior Software Engineer. As a key technical ... Developing RESTful APIs (using frameworks such as FastAPI) secured by OAuth2/Auth * Integrating ...

Via

Senior Software Engineer

Somerville, MA · On-site

$133.70K - $176.20K/yr

An impressive mission requires an equally impressive Senior Software Engineer. As a key technical ... Developing RESTful APIs (using frameworks such as FastAPI) secured by OAuth2/Auth * Integrating ...

Klaviyo

Senior AI Engineer

Boston, MA · On-site

$113.50K - $155.90K/yr

As a Sr. AI Engineer at Klaviyo, you'll play a key role in designing and building scalable backend ... Proficient in Python and modern backend frameworks (FastAPI, Django preferred). * Experience ...

Klaviyo

Senior AI Engineer

Boston, MA · On-site

$113.50K - $155.90K/yr

As a Sr. AI Engineer at Klaviyo, you'll play a key role in designing and building scalable backend ... Proficient in Python and modern backend frameworks (FastAPI, Django preferred). * Experience ...

Klaviyo

Sr. Manager, Orchestrate

Boston, MA · On-site

$137.40K - $181.40K/yr

As the Senior Engineering Manager for Orchestrate, you will lead multiple teams responsible for the ... Django/FastAPI or similar) * Experience with cloud infrastructure (AWS), DevOps practices, and ...

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How much do senior fastapi developer jobs pay per hour?

As of May 30, 2026, the average hourly pay for senior fastapi developer in Boston, MA is $67.06, according to ZipRecruiter salary data. Most workers in this role earn between $56.92 and $75.19 per hour, depending on experience, location, and employer.

What are the key skills and qualifications needed to thrive as a Senior FastAPI Developer, and why are they important?

To thrive as a Senior FastAPI Developer, you need deep expertise in Python, RESTful API design, and experience building scalable web backends, typically supported by a degree in computer science or related field. Familiarity with FastAPI, Docker, cloud platforms (such as AWS or Azure), and CI/CD tools is highly valued, along with proficiency in testing frameworks. Strong problem-solving, leadership, and communication skills help you collaborate effectively with cross-functional teams and mentor junior developers. These skills enable the delivery of robust, efficient, and maintainable APIs that support business goals and high user demands.

What are some common challenges faced by Senior FastAPI Developers when scaling applications, and how can these be addressed?

Senior FastAPI Developers often encounter challenges related to managing high concurrency, optimizing API performance, and ensuring robust security as applications scale. To address these, it’s important to implement asynchronous programming practices, leverage efficient database queries, and utilize API gateways for better traffic management. Collaboration with DevOps and QA teams is also essential to automate deployments and monitor system health, ensuring smooth scaling and reliable user experiences.

What does a Senior FastAPI Developer do?

A Senior FastAPI Developer designs, develops, and maintains backend web applications using the FastAPI framework in Python. They are responsible for building scalable APIs, optimizing performance, ensuring security best practices, and integrating with databases and external services. Senior developers also mentor junior team members, contribute to architecture decisions, and collaborate closely with front-end engineers and stakeholders to deliver robust software solutions.
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Senior Fastapi Developer jobs near you
Senior AI Application Engineer

Senior AI Application Engineer

Klaviyo

Boston, MA

Other

Posted 26 days ago

Job description

At Klaviyo, the ARIA (Applications, Resources, Intelligence, and Automations) team is building the AI systems that transform how our employees work. We are looking for a Senior IT App Engineer to design, build, and scale production-grade LLM integrations and AI-powered automation tools from the ground up. This role sits at the intersection of applied AI research and full-stack software engineering. You will own everything from LLM integration architecture and RAG system design to CI/CD pipeline management and production observability. If you want to build AI that real people use at scale every day, this is the role for you.

How you'll make a difference:

  • Design and build LLM-powered applications: Architect and develop production-grade systems leveraging large language models (GPT-4, Claude, Mistral, Llama) for internal automation, knowledge retrieval, and intelligent workflow assistance.
  • Build and maintain AI integration pipelines: Design robust, scalable API integrations between AI models and internal systems such as HRIS, ticketing, CRM, and knowledge bases, ensuring reliability, low latency, and high availability.
  • Develop full-stack AI features end-to-end: Own the complete development of AI features across the stack from backend model orchestration and API layers to frontend interfaces that make AI accessible to non-technical employees.
  • Architect and manage CI/CD pipelines for AI systems: Build and maintain automated deployment pipelines for AI models and services, including model evaluation frameworks, A/B testing infrastructure, and safe rollout strategies.
  • Implement RAG and retrieval systems: Design and build retrieval-augmented generation systems grounded in Klaviyo internal knowledge, ensuring accuracy, relevance, and up-to-date responses at scale.
  • Evaluate and fine-tune AI models: Lead benchmarking, evaluation, and fine-tuning of foundation models for Klaviyo use cases, including prompt engineering and parameter-efficient fine-tuning techniques.
  • Establish AI engineering best practices: Define coding standards, testing frameworks, and architectural patterns for AI development at Klaviyo, enabling the team to ship reliable AI features consistently.
  • Build AI observability and monitoring tooling: Instrument AI systems with latency monitoring, output quality evaluation, hallucination detection, cost dashboards, and production alerting.
  • Collaborate with Product and Data Science: Work closely with PMs, data scientists, and ML engineers to translate requirements into technical implementations, maintaining a tight feedback loop between experimentation and production.
  • Drive security and compliance in AI systems: Ensure AI integrations follow data privacy best practices, implement guardrails for sensitive data handling, and maintain compliance with Klaviyo security and governance standards.

Who you are: 

  • 3+ years of software engineering experience, with at least 2 years focused on building AI, ML, or LLM-powered systems in production.
  • Deep expertise with large language models such as OpenAI, Anthropic, Mistral, or Llama, and experience integrating them into production applications via API.
  • Strong full-stack engineering skills across Python (FastAPI, Flask, or Django) and TypeScript or JavaScript, with experience in modern frontend frameworks.
  • Proven experience designing and building CI/CD pipelines for software or ML systems using tools such as GitHub Actions, Jenkins, or CircleCI.
  • Experience with RAG systems, vector databases (Pinecone, Weaviate, pgvector), and embedding models.
  • Proficiency with cloud infrastructure (AWS, GCP, or Azure), containerization (Docker, Kubernetes), and infrastructure-as-code tools such as Terraform or Pulumi.
  • Experience with prompt engineering, model evaluation frameworks, and LLM observability tools such as LangSmith or Weights and Biases.

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