Senior Full Stack Engineer (Java & React)

Nexaminds is looking for a Senior Fullstack Engineer who is a true builder and thrives in fast-growing environments. You enjoy designing and shipping high-performance, large-scale systems and take full end-to-end ownership of complex initiatives, from ambiguous requirements to production at scale. You are passionate about system design, data-intensive architectures, and pushing modern engineering practices forward, while mentoring others and shaping engineering culture as the team grows.This role focuses on building and scaling a platform that powers enterprise partner ecosystems used by hundreds of companies. The system already handles tens of millions of rows and is designed to scale 10× from here.

Location: MEXICO (remote)

Qualifications we are looking for:

• Proven experience designing, building, and successfully scaling customer-facing production systems from a blank slat

• Deep, battle-tested PostgreSQL experience at scale, including partitioning, indexing, query optimization, and multi-tenant schemas

• Strong expertise in modern Java (21+) and Spring Boot, with natural use of streams, records, sealed classes, and virtual threads

• Comfort working across the full stack with modern React and TypeScript using functional components and hooks

• Hands-on experience with at least one major data warehouse (Snowflake, Databricks, BigQuery, or Redshift) and building analytics or BI features

• Strong commitment to functional programming principles, writing immutable-by-default, testable, and reliable code

• Ability to clearly explain complex technical trade-offs to both technical and non-technical stakeholders

• Motivation driven by sub-second query performance on large datasets and measurable customer impact

Job duties:

• Own the end-to-end architecture and implementation of major new product capabilities, from vague requirements to production at scale

• Design clean, evolvable database schemas and service boundaries for multi-tenant systems handling tens of millions of rows

• Build reliable data pipelines and analytics features on top of PostgreSQL, Snowflake / Databricks, and Kafka

• Push the stack forward using Java 21+, Spring Boot 3+, React + TypeScript, functional patterns, immutable data flows, and a strong focus on developer experience

• Make and clearly document complex technical trade-offs (consistency vs. availability, build vs. buy, normalization vs. denormalization, etc.)

• Set the standard for code quality, testing, observability, and performance

• Mentor other engineers and help shape engineering culture as the team scales.

Nice to have:

• Experience with Kotlin or another JVM language with a functional focus

• Contributions to open source, conference talks, or a well-written technical blog

• Previous experience in B2B SaaS, partner ecosystems, CRMs, or account mapping