Custom Java Development Services for Data-Intensive Systems
Build new platforms, modernize existing Java applications and keep production systems fast and dependable. Our engineers work across the Java stack, from data processing and integration to deployment and support.
Results from Java systems we have built
- 1,000,000,000
- financial transactions in under an hourFastPost accounting platform · developed for LegerityFastPost case study
- 300,000,000
- travel queries a dayHotel metasearch · 80% lower infrastructure costHotel search case study
- 65%
- less time to calculate flight schedulesProof of concept on production dataFlight schedule case study
Build, modernize and speed up your Java platform
Java engineers who put performance first and work as one team with yours, whichever of these four is your starting point.
New platform development
Java and Spring platforms for data processing, search, pricing and transaction workflows, designed from the domain model, the expected load and the systems they have to connect to.
Java modernization
Java 8, 11 or 17 moved to 21 or 25, Spring Boot 2.x or 3.x to Spring Boot 4, javax to Jakarta, with vulnerabilities fixed along the way and your releases continuing.
Architecture modernization
A monolith split into enforced modules, or into services where they pay off, and legacy parts replaced in slices while the old system keeps running.
Performance and scalability
Investigate bottlenecks under representative load. Improve response times, throughput or infrastructure use against an agreed baseline.
Modern Java and Spring stack we build on
Current long-term-support releases, kept current: a system that stays secure, fast and easy to hire engineers for.
Java 21 and 25
The two current long-term-support releases, with virtual threads, records and pattern matching in everyday use. Existing systems move up from 8, 11 or 17 before their support ends.
Spring Boot 4 and Spring AI
Spring Boot 4 on Spring Framework 7 for web services, batch, security and data access, and Spring AI for model calls and retrieval as ordinary Spring components.
Kafka and in-memory grids
Kafka 4, which runs without ZooKeeper, for event streaming; Hazelcast, Oracle Coherence or Apache Ignite where throughput and latency demand them.
PostgreSQL, Elasticsearch
PostgreSQL as the default relational store, measured before any cache is proposed; Elasticsearch where search relevance matters.
Cooperation models that best fit your project
Choose the cooperation model that fits your software needs, from building a data-intensive platform to a four-week AI integration pilot or a technical due diligence review.
| Offer | Price model | Duration | What you get |
|---|---|---|---|
| Data-intensive platform development | Time and materials with a ballpark range | Based on scope | Custom Java platforms for high-volume data processing, real-time search, pricing and analytics. |
| Application Modernization Sprint | Time and materials with a ballpark range | 6 to 12 weeks | A supported Java application baseline, with tested changes and a plan for the next phase |
| Performance Rescue | Time and materials with a ballpark range, against agreed SLO targets | 4 to 8 weeks | Measured latency and throughput improvements, with profiling evidence and validation against agreed SLOs |
| AI Integration for Java Systems | Time and materials pilot with a ballpark range; optional retainer | 4-week scoped pilot, then optional retainer | A scoped AI capability integrated with your Java application, with evaluation, access controls and a rollout decision |
| Managed Java Application Support | Monthly retainer with SLAs | Ongoing, quarterly review | Patching, dependency upgrades and a small-change budget for systems that must keep running |
| Java Team Extension | Monthly team fee | Ongoing, long-term | Senior Java engineers who join your team for the long term and bring our experience with them |
| Technical Due Diligence | Fixed fee by codebase size | 2 to 3 weeks | A written assessment of architecture, security, scalability, team and AI readiness for an investment decision |
Java engineering across complex business domains
Banking and fintech
Accounting, payments, lending and financial data platforms, including FastPost, a ledger that processes a billion transactions in under an hour, built over nearly ten years for Legerity.
Insurance
Policy, claims, rating and broker systems for insurers and MGAs. As Openkoda's implementation partner, we took Core Travel Insurance live in eight weeks.
Travel
Search, pricing and availability across changing inventories, including a hotel metasearch engine answering 300 million queries a day at 80% lower infrastructure cost.
Ecommerce
Pricing, search and recommendations, including Recostream, a recommendation engine answering in 20 to 30 ms that was acquired by GetResponse.
Real estate
Property data and business workflows with spatial data in the core model, such as a multi-tenant system for cost estimation, field surveys and project costing.
Stratoflow successfully customized the system according to the specific functionalities and without bugs reported. The team was commended for their adaptability in the work process and for their responsiveness.
Joshua BlavinsTech PM, Konekt Group
A clear scope, visible delivery and a planned handover
You speak with an architect from the first call, and the same engineers carry the work from the first iteration to handover.
Scoping call
Thirty minutes with an architect about the system, the business need and the constraints.
Written ballpark
Scope, assumptions, responsibilities, price model and duration in writing within a week, including how scope changes are handled.
Delivery in your repositories
Working increments every week, validated against agreed tests and performance measures, with your feedback steering the next iteration.
Handover or support
Documentation and knowledge transfer, or a support or team-extension arrangement if you would rather we kept working on it.
Before we start
Which Java technologies do you work with?
Java and Spring Boot form the core of our work, on Java 21 and 25 for new systems, with Spring AI for model integration. Depending on the system, we add Kafka, Hazelcast, Oracle Coherence, Apache Ignite, Elasticsearch and PostgreSQL. We select versions and deployment patterns around support requirements and measured needs.
Can you take over an existing application?
Yes. We first review the code, operating environment and available documentation, and agree the risks and the changes needed before we commit to delivery or support responsibilities. Evaluating a company you may acquire or invest in? A Technical Due Diligence review comes first.
How are engagements priced?
Scoped implementation projects are billed time and materials against a written ballpark estimate. Support uses a monthly retainer, and team extension uses a monthly team fee. We confirm the estimate once the scope and responsibilities are clear.
Who owns the code and works on it?
You own the commissioned code under the agreed contract, and work happens in repositories you control. Stratoflow engineers are directly employed; we do not subcontract delivery.
Do you build MVPs?
Yes, particularly for fintech and insurtech workflows that fit our Java expertise. We scope the first workflow before agreeing a build. A typical MVP engagement includes a one-week scoping phase followed by a four-week build, subject to readiness and scope.
What should we look for in a Java development company?
Evidence at your volume, and the engineers who produced it. A Java software development company should be able to show systems running under load, name who built them and say who will work on yours. As a Java application development company we build back-end platforms first: transaction processing, search, pricing and integration. We also work as a Java web development company where the platform needs portals and public APIs, but the load behind them is what we are chosen for.
Guides from our engineers
- Java
Java Best Practices for 2026: Modern Code and the Old Advice to Drop
Java 25 practices a build can enforce: records and sealed types, JSpecify null safety, BigDecimal and java.time, virtual threads, BOMs and scanning, Testcontainers, and the old advice to drop.
- Java
Java End of Life Dates, 2026 to 2033: What Ends When, and What October Changes
Every Java LTS in use today loses Oracle extended support between 2029 and 2033, and Oracle JDK 21 stops being free in production in October 2026.
- Modernization
Monolith to Microservices Migration Starts With a Modular Monolith
A decision test, the modular monolith as a first step, and how to extract Java services one at a time.
Discuss your Java platform
Bring the system, the constraint or the new product idea. We will help identify the right starting point and engagement model.