Do you rewrite from scratch or migrate incrementally?

Incrementally, by default. Big-bang rewrites freeze feature work and put the whole programme behind one high-risk cutover. We use strangler-fig and branch-by-abstraction patterns so the product stays releasable. A full rewrite is occasionally the right answer; the initial audit tells us when.

How do you change code that has no tests?

We write characterization tests first. They capture current behaviour, including odd edge cases, without claiming the behaviour is ideal. That gives us a reliable alarm when refactoring changes an output unintentionally.

Can modernization happen without a feature freeze?

Yes. That is a core design constraint. Stable facades and small migration seams allow your product team to keep shipping while modernization proceeds in parallel. There may be short, planned cutover windows for specific data changes, but not a six-month branch or roadmap freeze.

What happens to the existing database and data?

We map ownership first, then use backfills, dual writes, shadow reads, and reconciliation reports where appropriate. The new path is proven consistent before it becomes authoritative, and the old store remains available until rollback risk is acceptably low.

How do we know a cutover is safe?

The new path runs in parallel, receives real or replayed traffic, and has its outputs compared against the old path. We define acceptance thresholds in advance, instrument both sides, and rehearse rollback before changing production routing.

How long does legacy modernization take?

It depends on system size and the number of seams, but meaningful value should ship in weeks, not only at programme end. We normally structure the work as a sequence of independently releasable milestones over one or more quarters.

Will our team be able to maintain the new system?

Yes. We build in your infrastructure, document decisions and runbooks as we go, and pair with your engineers during migration. The target architecture is selected for operational fit and hiring reality, not novelty.

Incremental transformation

Legacy Modernization

We take aging codebases onto a supported, maintainable stack without betting the company on a rewrite. The old system keeps running while we replace it one proven seam at a time.

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Certified partnerships

Rated by clients and team

Clutch

What you get

A safer system after every release

Not a rewrite hidden on a long-lived branch. Every milestone reduces operational risk in production and leaves the codebase easier to change.

Incremental migration plan

A seam-by-seam roadmap that keeps the current system running while modern capabilities replace it in production.

Characterization test harness

Golden-master and contract tests that capture what the legacy system actually does before we change its internals.

Supported modern stack

End-of-life frameworks, runtimes, and build tooling replaced with a maintainable baseline your team can hire for.

Safe data migration

Backfills, dual writes, shadow reads, and reconciliation checks before any old data path is retired.

Stable integration boundaries

Adapter APIs and anti-corruption layers that stop new services inheriting old-system assumptions.

Reversible cutovers

Feature-flagged releases, parallel-run windows, observability, and a rehearsed rollback for every migration step.

Delivery

How we modernize legacy systems

Stage 1
Map the system and the risk
We audit architecture, dependencies, data ownership, deployment paths, failure modes, and the areas nobody wants to touch.
Stage 2
Build the safety net
Characterization tests, observability, and stable boundaries go in before migration work starts. We need to detect changed behaviour, not hope for it.
Stage 3
Migrate one seam at a time
Each capability moves behind a facade, runs alongside the legacy path, and proves itself on real traffic before cutover.
Stage 4
Cut over and remove dead code
After reconciliation and a rollback rehearsal, traffic moves to the new path and the old one is decommissioned so the system genuinely gets smaller.

Replace the system one proven seam at a time

The operating rule

No irreversible switch-flips

Every migration slice must be observable, comparable, and reversible before it receives full production traffic. If we cannot explain how to roll it back, it is not ready to cut over.

Parallel run

Output reconciliation

Rehearsed rollback

The result

A codebase your team wants to work in

Modern frameworks, clean boundaries, tested behaviour, and deployment paths that work. The legacy system shrinks with every milestone until it is either gone or reduced to a thin, well-understood shell.

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Fit

Is modernization the right intervention?

Best for

A revenue-critical product depends on unsupported frameworks or runtimes
Feature delivery is slowing because every change touches fragile shared code
You need to move cloud, database, or architecture without a long feature freeze
Security and compliance reviews are blocked by abandoned dependencies or opaque data flows

Not for

The system is healthy and only needs routine dependency updates
There are no tests, no production users, and a clean rebuild is plainly cheaper
You want a cosmetic frontend refresh without addressing the underlying platform
You need an emergency stabilisation first: start with Project Rescue or a Tech Audit

Related services

Start at the right point

Tech Audit

Map architecture, debt, security, and migration risk before committing to the modernization programme.

Explore service →

Project Rescue

Stabilise a failing or stalled system first, then modernize it from a known-good operational baseline.

Explore service →

Embedded Squad

Run a multi-quarter migration alongside your internal engineers with a dedicated senior pod.

Explore service →

Testimonials

What founders say after the build

Verbatim quotes from teams we shipped to production. We publish testimonials with written sign-off on file.

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Recorded client call
“I find him very nice to work with and he actually delivers a very good quality. So I am really happy with him.”
Noa van der Veen · Strategy and operations, CheckyPro
Recorded client call
“I very much respect the knowledge that you have. You have a lot of things, just in our few communications, that no one else has mentioned. No one else has even made me think about them.”
Mirinda Scott · Founder, AI Change Mangement
SkinOS / 2250.care
“The team treats our roadmap like their own. Every standup felt like working with our own engineers, not an outside vendor.”
SkinOS team
Clinical product, SkinOS / 2250.care
Recorded client call
“You're doing very, very well... the confidence that you're building with me — the full product is what I want to go with.”
Evan Kerivan · Founder & CEO, Restaurants Insightful
CheckyPro
“They told us what NOT to build. That single conversation re-shaped six months of roadmap and saved us a lot of money.”
CheckyPro team
Operations, CheckyPro
Recorded client call
“You guys seem switched on and like you know what you're doing. I've got a good feeling about it.”
Dan Cameron · Founder, Self-image
Recorded client call
“You guys take a lot of pride and ownership in the work.”
Hamza Tariq · Co-Founder, GoldenEye
PixelFox
“They shipped the production version of what our previous agency had been promising for nine months, without the weekly excuses.”
PixelFox team
Founders, PixelFox
Recorded client call
“I find him very nice to work with and he actually delivers a very good quality. So I am really happy with him.”
Noa van der Veen · Strategy and operations, CheckyPro
“I had a large project built that needed a very specific understanding and the project was executed perfectly. Great design, great code, no bugs and anything I needed was done incredibly professionally. I would highly recommend and I will definitely be coming back with my…”
Verified client
Israel
$4,000+ · 11 monthsVerified client review
“We approached several sellers in our search to get an app developed for our Shopify store. I had a very clear idea in my mind what we wanted and, through [their] expert questioning, [they] absolutely 'got it'. This was further proved through delivery of a…”
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United Kingdom
$1,500–$2,000 · 4 weeksVerified client review
“We're working on a Shopify app that retrieves book data from our API and helps online stores and booksellers create book listings faster. This time, we needed to improve the app design and fix functionality issues. In general, we're satisfied with the service and plan…”
Barbara Hartman
Repeat client · United States
$400–$600 · 3 weeksVerified client review
“This was a special request where we needed to rush this development. [They] complied and finished everything at the agreed time, and even worked until 2AM [their] local time in order to finish this on time. [They] went the extra mile for us with this…”
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Canada
Verified client review
“[They were] very patient as we figured out exactly what we needed our app to do. [They were] able to get all the functionality we required, communicated well, and [were] upfront about the cost. We'll definitely be coming back for future projects!”
Ben McLellan
Canada
Verified client review
“Absolutely fantastic work. This was a tricky app, and [they] did great work. [They] really know [their] way around Shopify and the process for developing a Shopify app, which was a great help to me! [They're] motivated and committed, and delivered a very high-quality app.…”
Lisa Zigel
Israel
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“I am very pleased to have worked with [them]! [They were] very detailed and delivered me perfection in an app! I look forward to working with [them] again!”
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United States
$3,000–$4,000 · 2 monthsVerified client review
“Amazing service. Amazing time. Took all input and made the site great even with minor changes along the way. Will certainly try to use again if I'm lucky enough to have [them] work with me again. Thank you for everything.”
Gabriel Muller
United States
Verified client review
“Very fast and thorough. [They] did exactly what I asked and then went the extra mile to tie up a couple of loose ends. I'm really pleased with the speed and efficiency, and would certainly recommend [them]. Thank you for your help and highly professional…”
Danny Venn
Cambodia
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“[They understand] the problem so well and deliver the results super quick. I'll not hesitate to say that I've found a gem. One thousand percent recommended!”
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Pakistan
Verified client review
“Very positive experience. [They are] diligent, hardworking, and [have] good communication skills. Highly recommended.”
Max Hawthorne
United States
Verified client review
“[They were] very patient, [and] prepared to go the extra mile so I got the result I wanted. Highly recommended.”
Carey Heazlewood
Australia
Verified client review
“The project was not easy, literally. [They] did hard work on our project and finished as expected. Would like to work on upcoming new features together. Thank you.”
Erica Yagelsk
United States
Verified client review
“[They are] reasonable, meticulous, [have] a great sense of design, and [are] very responsive. I really enjoyed working with [them] and [they] delivered a beautiful website for me.”
Verified client
United States
Verified client review
“Extremely patient and did not stop until what I needed was delivered. Excellent partner to work with!”
R. Mendoza
United States
Verified client review
“I didn't expect such great service from someone I found without a referral. I got lucky and I hope to work with [them] again in the future.”
Verified client
United States
$1,500–$2,000 · 10 daysVerified client review
“Bought this to create a website for my startup company. Results were above and beyond what I was expecting! Quick to answer, and always gave great input and ideas!”
J. Leonard
United States
Verified client review
“We are very impressed with the service and the delivery and will use them again!”
Alexander Ekdahl
Sweden
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“Great work and completed exactly as requested!”
Margie Odom
United States
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“100% satisfied. Got more than expected.”
Christine Malo
Canada
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“Great communication, great result.”
Havsund
Germany
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“Thank you so much for such outstanding work.”
Valdour
Spain
Verified client review

4.6/5across 58 verified client reviews.Read them all at source