Senior Software Engineer - Activation APIs

It takes powerful technology to connect our brands and partners with an audience of hundreds of millions of people. Whether you're looking to write mobile app code, engineer the servers behind our massive ad tech stacks, or develop algorithms to help us process trillions of data points a day, what you do here will have a huge impact on our business—and the world.

About the Team

Our platform is the foundational identity and data layer for 900M+ monthly active users, serving 2.5B+ profiles at massive scale. We are building a predictive, identity‑centric insights engine ensuring our audience is understood with precision to deliver hyper‑personalized experiences and advertising solutions across all our digital properties.

Our mission centers on first‑party data strategy: capturing, enriching, and activating audience signals to build a 360‑degree view of every user. We operate under a Privacy‑by‑Design philosophy, adhering to global regulations (GDPR, CCPA) and industry security standards, while leveraging a cloud‑native stack across GCP and AWS and modern MLOps practices to deliver measurable business impact.

About the Role

As a Senior Software Engineer, you will build and optimize high‑performance production APIs that serve millions of requests per second with sub‑10ms latency. These APIs are critical infrastructure enabling our personalization and advertising systems to access the 2.5B+ profile dataset in real‑time, directly impacting hundreds of millions in annual revenue and user experience quality.

You will develop API endpoints integrating with downstream systems and applications, ensuring reliable, low‑latency access to user profile data, audience segments, and enrichment signals. Your work requires balancing extreme performance requirements (sub‑10ms p99 latency) with data privacy compliance, cost efficiency, and production reliability at massive scale.

This role demands deep expertise in high‑performance API development, distributed caching strategies, and production systems engineering. You will collaborate closely with Product, Data Platform, and Infrastructure teams while taking ownership of critical API components that serve as the backbone of our data activation strategy.

Key Responsibilities

• Develop and optimize high‑performance REST and gRPC APIs for user profile activation, audience segment retrieval, and enrichment data access.
• Implement API endpoints integrating with downstream systems and applications, ensuring sub‑10ms p99 latency at millions of RPS.
• Build comprehensive monitoring and alerting systems tracking API latency, throughput, error rates, cache hit rates, and SLA compliance (99.99% availability).
• Optimize data access patterns using Cloud Spanner and Valkey (Redis) distributed caching for ultra‑low‑latency response times.
• Write extensive unit tests, integration tests, load tests, and API documentation following OpenAPI/Swagger specifications.
• Collaborate with Infrastructure teams on API deployment strategies, autoscaling policies, and production operations in GCP (Cloud Run, GKE).
• Participate in on‑call rotation supporting production API availability, incident response, and performance troubleshooting.
• Implement API authentication, authorization, rate limiting, and quota management ensuring secure access to sensitive user data.
• Improve API efficiency through profiling, performance analysis, and optimization of database queries, caching strategies, and serialization.
• Mentor junior engineers on API design patterns, production best practices, and distributed systems principles.
• Troubleshoot production incidents, perform root cause analysis, and implement reliability improvements to prevent recurrence.
• Contribute to API design reviews, code reviews, and technical discussions improving team practices and code quality.

Required Qualifications

Education

• Bachelor's degree in Computer Science, Engineering, or related technical field.

Experience

• 5+ years software engineering experience building production systems.
• 3+ years hands‑on experience developing and operating high‑performance APIs or distributed services.
• Proven track record delivering high‑quality, well‑tested code on schedule.

Technical Skills

• Strong proficiency in Java, Python, or Go for backend API development.
• Hands‑on experience with REST API design, gRPC, authentication (OAuth 2.0, JWT), and rate limiting.
• Experience with Google Cloud Platform: Cloud Run, GKE, Cloud Spanner, Memorystore (Redis), Cloud Load Balancing, or AWS equivalents.
• Understanding of distributed systems principles: caching strategies, load balancing, database optimization, fault tolerance.
• SQL proficiency and experience with distributed databases (Spanner, CockroachDB, TiDB) or relational databases at scale.
• Familiarity with API monitoring and observability: metrics, logs, traces, SLIs/SLOs, error budgets.

Competencies

• Demonstrated ability delivering well‑scoped technical solutions on schedule with minimal guidance.
• Strong problem‑solving and debugging skills in production environments.
• Excellent collaboration and communication abilities working with cross‑functional teams.
• Team‑level impact with ability to influence technical decisions within immediate team.
• Understanding of data privacy compliance (GDPR, CCPA) in API design and implementation.

Preferred Qualifications

• Experience with Cloud Spanner, Valkey/Redis, or other low‑latency data stores in production.
• Knowledge of API gateways (Apigee, Kong, Ambassador) and service mesh (Istio, Linkerd).
• Prior experience in adtech, audience platforms, or high‑scale consumer services (millions of RPS).
• Understanding of privacy compliance requirements (GDPR, CCPA) and secure API design patterns.
• Familiarity with OpenAPI/Swagger specifications, API testing frameworks (Postman, k6, Locust).
• Experience with chaos engineering, load testing, and performance benchmarking.
• Contributions to open‑source projects, technical blogging, or API design communities.
• Self‑driven, detail‑oriented, excellent multitasking abilities in fast‑paced environments.

Compensation & Benefits

Compensation ranges from $128,250.00 to $266,875.00 per year, varying by location, skills, and experience. The package may include discretionary annual bonuses or commissions. Benefits include healthcare, a 401(k), backup childcare, education stipends, and more.

Equal Opportunity Statement

Yahoo is proud to be an equal‑opportunity workplace. All qualified applicants will receive consideration for employment without regard to age, race, gender, color, religion, national origin, sexual orientation, gender identity, veteran status, disability or any other protected category. Yahoo will consider qualified applicants with criminal histories in a manner consistent with applicable law. Yahoo is dedicated to providing an accessible environment for all candidates during the application process and for employees during their employment.