Senior Java Backend Developer

Position: Sr Java Backend Developer 
Location: Phoenix, AZ (Onsite)
Duration: Long Term
Client: Amex
Exp: 11+ Year
Visa: H1B

Job Description:

Summary:

We are looking for a highly experienced Senior Java Engineer with strong hands-on coding expertise, deep system design knowledge, and real-world experience building scalable, secure, and reactive applications. The ideal candidate should be comfortable with advanced Java concepts, Spring ecosystem, distributed systems, and modern architectural patterns.

Must-Have Skills & Experience
Core Java & Backend Development

12+ years of hands-on Java development experience
Strong expertise in Core Java (Java 8 & Java 11)
In-depth practical knowledge of Java backend with AI

In-depth understanding of:

Java Streams (Sequential vs Parallel)
Why streams are used and performance benefits
Functional Programming concepts
Strong hands-on Java coding ability (interview-level coding expected)
Spring & Reactive Stack
Spring Boot (REST APIs, configuration, best practices)
Spring Batch
Reactive Java:
Spring WebFlux
Vert.x
Strong understanding of:
block() vs subscribe() methods
Reactive programming principles
Security & Authentication
Spring Security
OAuth 2.0
JWT Token based authentication & authorization
Databases & Data Access
NoSQL – MongoDB

Strong understanding of:

Database configurations
Data access patterns
SQL Joins and types of joins (inner, left, right, full) with explanations
Clear explanation of which DBs were used and why
System Design & Architecture
Strong knowledge of System Design Concepts
Design Patterns, including:
Singleton (why it’s used)
Factory Pattern
Strategy Pattern
Distributed system patterns:
Circuit Breaker Pattern
Saga Transaction Pattern
CPRS Pattern
Concurrency & Performance
Thread Safety concepts
Synchronization and locking mechanisms
Usage of AtomicInteger and why it is preferred
Strong understanding of multithreading challenges
Messaging & Streaming
Apache Kafka (producer, consumer, real-world usage)
Algorithms & Problem Solving
Strong foundation in Algorithms
Ability to explain problem-solving approach clearly
REST & API Development
Ability to write and explain Java code defining REST APIs using Spring Boot
Hands-on experience building scalable RESTful services
Behavioral & Scenario-Based
Ability to explain challenging technical situations
Clear articulation of how issues were handled and resolved
Strong communication and ownership mindset

Nice-to-Have Skills

Previous experience with American Express (Ex-Amex)
Experience working in large-scale enterprise environments
Exposure to high-availability and fault-tolerant systems
Cloud exposure (AWS / Azure) – added advantage
Experience mentoring or guiding junior developers
Interview Expectations
Deep Java & Spring conceptual questions
Live Java coding
System design discussion
Multithreading & concurrency scenarios
Reactive programming use cases
Real-world architecture and problem-solving discussions