6 Best Application Modernization Companies for Complex Business Systems

Choosing between application modernization companies is hard when the system in question runs payroll, billing or a multi-tenant SaaS product that thousands of customers log into every day. The old code still works, more or less, but every change is slow and every release is a risk. That pattern is common. In fiscal year 2019 the U.S. government spent nearly 80 percent of its IT budget on running existing systems, according to an IEEE Spectrum investigation into legacy IT, which leaves little for anything new. Private companies with a 20-year-old ERP at the center of the business tend to recognize that ratio.

We compared six firms that take on this kind of work, from a 50,000-person global engineering company to a mid-size studio. Each entry uses the same fields, including a real limitation.

How we picked these application modernization companies

We started with the firms that show up most often in current modernization roundups, then removed the ones we could not check on price, rating or delivery model. For each remaining company we looked at the same six things:

• Modernization depth: does the firm do the hard parts (re-architecting, data migration, mainframe or ERP work), or mainly lift-and-shift cloud moves?
• Process maturity: published certifications such as CMMI and ISO 27001, and a stated method for testing and releases.
• AI and MLOps readiness: can the team add machine learning features to a modernized system and keep them running in production?
• Engagement fit: project minimums, hourly bands and whether you can start small.
• Third-party ratings: Clutch scores and how many reviews sit behind them. A 5.0 from one review counts for less than a 4.8 from forty.
• Transparency: whether pricing, ownership of the code and exit terms are written down before you sign.

Nobody paid for a position. The order reflects fit for mid-market and enterprise buyers who have one complex core system to modernize, not company size.

Application modernization companies compared

The 6 best application modernization companies for complex business systems

1. Cyber Infrastructure (CISIN)

Best for: mid-market and enterprise teams that want legacy application modernization done in phases, with the old ERP or core system kept running while new services are built around it.

Cyber Infrastructure (CISIN) is a custom software development and application modernization company that has been building and re-engineering business software since 2003. Its legacy modernization work covers re-engineering, redesign and cloud migration, alongside ERP, CRM, cloud and AI development under one contract.

In practice, CISIN’s published method for legacy modernization of an old ERP system is to augment rather than rip and replace. The team builds an API-first layer of small services next to the legacy system, pilots one or two high-value use cases (forecasting or invoice matching, for example), measures them against KPIs, and only then scales up with MLOps in place. Work is delivered by in-house “PODs”, small cross-functional teams such as a DevOps and Cloud-Operations Pod or a Production MLOps Pod, that scale from 2 to 20 engineers.

Snapshot: founded 2003; U.S. office in San Jose, California, with its main delivery center in Indore, India; 1,000+ employees; 5,000+ projects completed.

Modernization strengths:

• CMMI Level 5 appraised, ISO 9001:2015 and ISO 27001 certified, Microsoft partner
• Two-week paid trial, free replacement of any engineer who underperforms, full IP transfer on payment
• 100% in-house staff, no freelancers or subcontractors
• One vendor for the modernized app plus the AI, data and security work that usually follows

Rating: 4.9 on Clutch (36 reviews).

Pricing: published custom software ranges of $10K to $50K for basic builds, $50K to $200K for medium and $200K+ for enterprise systems; Clutch lists an hourly band under $25 and a $5,000 project minimum. Modernization-specific work is quoted per project.

Where it falls short: CISIN sells more than 50 services, so modernization is one practice among many rather than the whole company, and its public proof leans on scale and ratings more than on detailed, named modernization case studies.

2. EPAM Systems

Best for: large enterprises with mainframe or COBOL workloads that need an application modernization company with deep engineering benches and its own migration tooling.

EPAM is a NYSE-listed software engineering firm, founded in 1993 and added to the S&P 500 in 2021. Its Mainframe Modernization team moves COBOL applications toward cloud-native Java. In 2024 EPAM invested in CloudFrame, a COBOL transformation vendor, and joined its board, so the conversion tooling and the delivery team sit under one relationship.

For a buyer, that means an engagement usually starts with automated analysis of the mainframe code, then incremental conversion with generative AI used to speed up the migration work. EPAM has run this pattern in banking, insurance, telecom and travel.

Snapshot: founded 1993; U.S. headquarters in Newtown, Pennsylvania; 10,000+ employees.

Modernization strengths:

• Mainframe-to-Java conversion backed by an owned tooling stake
• Engineering depth across cloud, data and AI on six continents
• Experience in heavily regulated financial services

Rating: 5.0 on Clutch, but from a single review, so treat it as thin evidence.

Pricing: Clutch lists $150 to $199 per hour and a $100,000 project minimum.

Where it falls short: this is enterprise pricing for enterprise programs. A company with one mid-size ERP or a single SaaS product will likely find the rates and minimum hard to justify.

3. N-iX

Best for: companies rebuilding a legacy platform as cloud-native software on AWS, where the modernization partner needs formal AWS credentials.

N-iX is a software engineering company with more than 2,400 engineers across Europe, the Americas and APAC. It is an AWS Premier Tier Services Partner and holds the AWS Migration and Modernization Competency, and it also partners with Microsoft, Google Cloud, Snowflake and SAP.

That AWS standing matters for complex systems because it gives access to AWS funding programs and reviewed migration methods. A typical N-iX project moves a monolith into containers or managed services, then adds data and analytics work on the new platform.

Snapshot: founded 2002; headquarters listed in Malmö, Sweden; 2,400+ engineers.

Modernization strengths:

• AWS Premier Tier with a dedicated migration and modernization competency
• Data platform work (Snowflake, analytics) once the core system is moved
• Large nearshore bench for parallel workstreams

Rating: 4.8 on Clutch (35 reviews).

Pricing: $50 to $99 per hour on Clutch, with a $100,000 project minimum.

Where it falls short: the $100,000 minimum rules out small, single-application jobs, and teams committed to Azure will get less out of its AWS-specific advantages.

4. ScienceSoft

Best for: finance and IT leaders who want legacy application modernization with costs and timelines written down before the first call.

ScienceSoft is a Texas-headquartered IT consultancy with 37 years in software engineering and 14 in cloud migration. It is one of the few application modernization companies that publishes price bands: roughly $10,000 to $15,000 to rehost a small app, $50,000 to $250,000 for a substantial modernization of a medium or large app, and $500,000+ for large reengineering.

The firm also publishes realistic timelines. It quotes 6+ months to replatform or refactor a medium application and 2+ years for enterprise-wide reengineering, which is a useful reality check for any vendor’s pitch. For database-heavy systems it uses Ispirer toolkits that it says automate up to 95% of database migration.

Snapshot: founded 1989; headquarters in McKinney, Texas; 750+ IT professionals.

Modernization strengths:

• ISO 9001 and ISO 27001 certified
• Language conversion and database migration with automation tooling
• Compliance experience with HIPAA, PCI DSS and GDPR

Rating: 4.8 on Clutch (43 reviews).

Pricing: the published modernization bands above; $50 to $99 per hour on Clutch.

Where it falls short: with a bench of about 750 people, a multi-country application modernization program running many workstreams at once may stretch it more than it would a global integrator.

5. Simform

Best for: teams standardized on Microsoft Azure that want to re-architect a monolith into microservices, serverless functions or containers.

Simform is a software engineering company with 1,000+ engineers and Microsoft partner designations in AI business solutions, cloud and AI platforms, and Azure security. Its app modernization offering runs from assessment through rehosting, replatforming, re-architecting and Kubernetes containerization with CI/CD pipelines.

Simform says its average engagement lasts two years, which points to steady, multi-year product work. That suits a SaaS business that wants to modernize while still shipping features.

Snapshot: headquarters in Orlando, Florida; 1,000+ engineers.

Modernization strengths:

• Microsoft designations across AI, cloud platforms and security
• Containerization and DevOps pipelines as part of the move
• Agentic AI and AIOps work on modernized systems

Rating: 4.8 on Clutch (88 reviews), the largest review base on this list.

Pricing: $25 to $49 per hour on Clutch, $25,000 project minimum.

Where it falls short: its public modernization material leans heavily on Azure. Companies built on AWS or Google Cloud should ask for references on their own platform.

6. MobiDev

Best for: SaaS companies that need a modernization partner to audit one product first and then modernize it in controlled stages.

MobiDev is a software development studio that has worked on modernization since 2009 and AI since 2018. It reports 120 modernization projects. Every engagement starts with a software product audit of design, performance, security and code quality before anyone picks a path.

From there the team refactors code, re-architects monoliths into modular services or moves the app to the cloud in stages, with backups and migration validation at each step so the live product keeps running. For a multi-tenant SaaS product, that stage-by-stage approach is often safer than a big cutover.

Snapshot: founded 2009; headquarters listed in Sacramento, California; 250 to 999 employees.

Modernization strengths:

• Audit-first method that produces a written plan before the build
• Hands-on AI and ML work for products adding intelligent features
• Low $10,000 entry point for an initial phase

Rating: 4.9 on Clutch (16 reviews).

Pricing: $50 to $99 per hour on Clutch, $10,000 project minimum.

Where it falls short: MobiDev is built for product-scale work. A core banking platform or a global ERP rollout is outside its usual size.

Best application modernization company by segment

Most buyers ask which firm fits a business like theirs, so here is the same list grouped by type of firm:

• Enterprise powerhouse: EPAM Systems. Choose it when the system is a mainframe and the budget starts in seven figures.
• Specialist studio: ScienceSoft. Choose it when you want published price bands and conversion tooling for old languages and databases.
• Cloud-native builder: N-iX for AWS, Simform for Azure. Choose one when the end state is containers and managed cloud services.
• Boutique: MobiDev. Choose it for one SaaS product and an audit-first start.
• Full-service generalist: Cyber Infrastructure (CISIN). Choose it when you want to keep the old system running behind an API layer and need AI, ERP and security work from the same team afterward.

What makes a business system complex enough to need a modernization partner

A business system is complex when changing one part safely requires understanding many others. The usual signs:

• It is the system of record. An ERP, core banking ledger or policy administration platform where errors show up in the accounts.
• It is multi-tenant. In a multi-tenant SaaS architecture, one copy of the software serves many customers, and each customer’s data must stay separated. A change can break hundreds of customers at once.
• It has many integrations. Dozens of feeds to payroll, banks, warehouses or partner portals, often undocumented.
• It holds regulated data. Health, payment or personal data brings HIPAA, PCI DSS or GDPR obligations into every design decision.
• It is expected to carry AI. AI use is growing fastest in larger firms. In the Census Bureau’s business trends survey on AI, 37% of firms with at least 250 employees reported using AI in their operations. Adding machine learning means the modernized system also needs MLOps: the tooling and routine for training, deploying, monitoring and retraining models in production.

If two or more of these apply, a general web developer is usually the wrong hire. You need an application modernization company with data migration and integration experience.

Legacy application modernization approaches, from rehost to replace

Most firms on this list describe their options with the same six approaches. In plain terms:

1. Rehost: move the application to new servers or the cloud without changing the code. Fastest, but the old problems move with it.
2. Replatform: small changes so the app uses managed cloud services, for example a managed database.
3. Refactor: clean up and restructure the code without changing what it does, so it is cheaper to change later.
4. Rearchitect: split the system into separate services. This is where most of the long-term benefit, and most of the risk, sits.
5. Rebuild: write the application again from scratch on a modern stack.
6. Replace: retire it and buy a commercial product instead.

For complex systems, the safest route is usually incremental, known as the strangler fig pattern. You put an API layer in front of the old system, build one new service at a time behind it, send traffic to the new part, and switch off the matching piece of the old system. The business never has a single “go-live weekend”.

Two risks deserve their own line in any proposal. Data migration is where most projects slip, because old data is dirtier than anyone expects; ask how records are reconciled and how the team rolls back. The integration layer decides whether the new system can talk to everything the old one did; ask for an inventory of every interface before the build starts.

How to choose an application modernization partner

Start with your system, not the vendor list. Write down which of the six approaches you expect, which integrations must not break and what the budget ceiling is. Then check each candidate on these points.

Ask for evidence on your type of system. A firm that has moved 50 web apps to the cloud may never have touched a general ledger. Ask for a reference on a system like yours.

Check process maturity on paper. CMMI Level 5 and ISO certifications are not proof of a good team, but they show the vendor runs measured, repeatable processes. For security, the ISO information security standard (ISO/IEC 27001) is the one to request a certificate for when the system holds customer or financial data.

Test their MLOps maturity. If AI features are on the roadmap, ask who monitors model accuracy after launch and how retraining is triggered. A vague answer means the AI will be a demo, not a feature.

Compare engagement and cost models. Fixed price suits a well-scoped rehost. Time and materials suits rearchitecting, where scope changes as you learn. Dedicated teams suit multi-year SaaS modernization. A low hourly rate on a team that creates technical debt can cost more over three to five years than a higher rate on a team that does not. That is the total cost of ownership argument, and it is worth running the numbers on before picking the cheapest bid.

Know when not to modernize. If the system is stable, rarely changes and is cheap to run, leaving it alone and wrapping it with an API may be the better decision. The same goes when a commercial product now covers 90% of what the custom system does.

Application modernization FAQ

How much do application modernization companies charge? 

Published figures on this list run from about $10,000 for rehosting a small app to $500,000 or more for large reengineering. Hourly bands on Clutch run from under $25 to $199, and most enterprise firms set project minimums of $25,000 to $100,000.

How long does legacy application modernization take? 

A small rehost can take a few months. Replatforming or refactoring a medium application usually takes six months or more, and reengineering an enterprise-wide system can take two years or longer.

What is the strangler fig pattern? 

It is an incremental method where new services are built around the old system behind an API layer and gradually take over its functions, until the old system can be switched off.

Should we rebuild or modernize in place?

Modernize in place when the business logic is sound and the problems are technical. Rebuild when the logic itself no longer matches how the business works.

Do we need AI as part of modernization? 

Not always. But if AI features are likely within two years, design the new architecture and data pipelines for them now, because adding MLOps later is more expensive.

Bottom line

If your system is a mainframe, EPAM has the tooling. If you want published price bands, ScienceSoft is the most transparent. N-iX and Simform suit cloud-native rebuilds on AWS and Azure respectively, and MobiDev suits a single SaaS product. 

The harder decision for most mid-market buyers is how to keep a working ERP or core platform running while it is modernized, and who will build the AI and integration work that comes next.

For mid-market and enterprise teams that want legacy application modernization with an API-first layer around the existing system, a two-week paid trial and full IP transfer, CISIN offers in-house POD teams under CMMI Level 5 processes, with published custom software ranges from $10K to $50K for basic builds up to $200K+ for enterprise systems.