About Zealous System
Zealous System is a trusted technology leader in software development and IT consulting services, having expertise in mobile app development for various platforms – iOS, Android.
Services
Mobile App Development
Web Development
UI-UX Design
Cross Platform App Development
Web Design
Android App Development
Hybrid App Development
Zealous System Reviews
Write a ReviewA technology partner worth every penny of the investment
Sinead Gallagher / Director of Engineering - Celtic Digital Ltd
Verified
Sep 01, 2025
Sep 01, 2025
Project summary: Peak season traffic had been exposing architectural weaknesses in our platform for two years. We could no longer afford to enter a promotional period hoping for the best.
The technical quality of the work is the easiest thing to praise, but what I want to highlight is the communication culture on this team. Every question got a same-day response. Every risk got flagged before it became an issue. When we needed to change direction mid-project — a business decision on our side — they absorbed the change professionally, requoted fairly, and kept momentum going. That flexibility is something you cannot assess in a proposal and it turned out to be one of the most valuable things about working with them.
PROS
Business-aware approach to every technical decision, strong project governance, fast turnaround on feedback, zero drama during a genuinely complex engagement
CONS
The initial project brief document they required was more detailed than we were used to providing, but in hindsight that rigour was part of why the project ran so smoothly
Project TypeEmbedded Systems Development
IndustryRetail & E-commerce
Project Cost$10,000 to $49,999
DurationDec 2024 – Jan 2026
Questions & Answers
Please describe your company, your role, and the industry you operate in.
Celtic Digital Ltd operates across the Retail & E-commerce sector with offices in Cork, Ireland. In my capacity as Director of Engineering I oversee both the strategic and operational technology agenda. We are a growth-stage business that needed a development partner capable of scaling with us rather than constraining us.
What specific problem or business challenge led you to hire this company?
Our Retail & E-commerce regulatory environment had changed and the compliance timeline was non-negotiable. We needed to rebuild specific components of our system to meet the new requirements and our internal team was already fully committed to the core product roadmap. Bringing in a specialist Embedded Systems Development partner was the only realistic path.
What services did the company provide for your project?
Primarily Embedded Systems Development, though the scope naturally touched adjacent areas. They handled architecture design, implementation, integration with our existing systems, performance testing under realistic load, and knowledge transfer to our internal team. The breadth of what they covered without requiring us to bring in additional vendors was one of the reasons the project ran efficiently.
Why did you choose this company over other providers you considered?
Their portfolio included two projects that were sufficiently close to our own brief in terms of complexity, Embedded Systems Development scope, and Retail & E-commerce context that we felt confident they understood what we were asking. The proposal was technically rigorous, the pricing was transparent, and the proposed team structure gave us senior engineers throughout rather than just for the pitch.
How clearly did the company understand your requirements and business goals?
The requirements understanding was solid from early on, aided by the fact that they had prior experience in the Retail & E-commerce sector and did not need us to explain domain context that a less experienced team would have required. That background knowledge shortened the discovery phase meaningfully and reduced the volume of clarification questions during sprints.
How was your overall experience with their communication and project management?
Communication was handled primarily asynchronously given the time zone difference between Cork, Ireland and the team's base, but it was managed so well that the gap rarely felt like a constraint. Written updates were clear and timely, escalations were handled promptly, and we never had to chase for a status update. The cadence was exactly right — enough to feel informed, not so much that it created overhead.
Did the company deliver the project on time and within your expected budget?
Yes on both counts. There was one sprint where a third-party integration took longer than scoped because of undocumented API behaviour on the vendor side. The team flagged it immediately, proposed two mitigation options, and we agreed on an approach that recovered the timeline within two weeks. That is how scope issues should be handled and rarely are.
What tangible results or business impact have you seen since the project was completed?
We went live three months ago. In that time we have not had a single P1 incident, our page performance scores have improved across every measure, and the feature we had deprioritised for years because the old architecture made it too complex to implement is now in our next sprint. The platform they built has opened up our roadmap in a way we had not anticipated.
What did you like most about working with this company?
Their ability to hold the business objective in mind alongside the technical task. I have worked with technically excellent agencies who lost the thread of what we were actually trying to achieve. This team never did. Every architectural decision, every trade-off conversation, every prioritisation discussion was anchored to the outcome we had agreed at the start.
Would you recommend this company to others, and would you work with them again?
I recommend them to anyone who asks and occasionally to people who do not. The combination of Embedded Systems Development expertise, Retail & E-commerce domain knowledge, and delivery discipline is genuinely difficult to find. We found it here and we intend to keep it.
Custom-built platform that became the backbone of our entire operation
Piotr Wojciechowski / Head of Development - Vistula Software Sp zoo
Verified
Mar 21, 2024
Mar 21, 2024
Project summary: We needed to connect our factory floor systems to our ERP to give operations management real-time visibility into production status, waste, and throughput.
Project governance was one of the things that impressed me most. We had a dedicated project manager who ran tight fortnightly sprints with clear acceptance criteria, a shared backlog that gave us full visibility at all times, and a change request process that was fair and transparent. Nothing slipped through the cracks, no bill shock at the end, and the final delivery matched the original scope document almost perfectly. In my experience that kind of discipline is genuinely uncommon.
PROS
Technical depth across the full stack, honest and timely communication, delivered exactly what was scoped without surprise additions to the invoice
CONS
Premium pricing compared to some of the alternatives we evaluated, but the quality of the output and the absence of rework costs made the investment straightforward to justify
Project TypeSoftware Development
IndustryManufacturing
Project Cost$150,000 to $499,999
DurationFeb 2025 – Aug 2025
Questions & Answers
Please describe your company, your role, and the industry you operate in.
Vistula Software Sp zoo operates across the Manufacturing sector with offices in Warsaw, Poland. In my capacity as Head of Development I oversee both the strategic and operational technology agenda. We are a growth-stage business that needed a development partner capable of scaling with us rather than constraining us.
What specific problem or business challenge led you to hire this company?
Our existing Software Development capability had accumulated years of technical debt that was slowing every new feature to a crawl. Incident frequency was rising, developer confidence was falling, and we knew a rebuild was overdue. We needed a partner with the depth to do it properly rather than apply another layer of patches.
What services did the company provide for your project?
Primarily Software Development, though the scope naturally touched adjacent areas. They handled architecture design, implementation, integration with our existing systems, performance testing under realistic load, and knowledge transfer to our internal team. The breadth of what they covered without requiring us to bring in additional vendors was one of the reasons the project ran efficiently.
Why did you choose this company over other providers you considered?
A direct referral from a peer who had used them for a comparable Software Development engagement in the Manufacturing space. That peer's experience had been excellent and their project profile was similar enough to ours that the recommendation carried real weight. Everything we found during our own evaluation reinforced that this was the right decision.
How clearly did the company understand your requirements and business goals?
The requirements understanding was solid from early on, aided by the fact that they had prior experience in the Manufacturing sector and did not need us to explain domain context that a less experienced team would have required. That background knowledge shortened the discovery phase meaningfully and reduced the volume of clarification questions during sprints.
How was your overall experience with their communication and project management?
Professional and efficient. We used a shared project management tool that gave our stakeholders visibility without requiring them to attend every meeting. The project manager had a clear escalation path and used it appropriately. The only time I needed to intervene directly was when I chose to, not because something had been missed.
Did the company deliver the project on time and within your expected budget?
Yes. I will note that the original timeline was aggressive and I had privately expected a slip. They managed to hold it by making smart sequencing decisions early on that I only fully understood in retrospect. The budget discipline was equally good — we received a single change request for scope we had introduced ourselves and it was priced fairly.
What tangible results or business impact have you seen since the project was completed?
We went live three months ago. In that time we have not had a single P1 incident, our page performance scores have improved across every measure, and the feature we had deprioritised for years because the old architecture made it too complex to implement is now in our next sprint. The platform they built has opened up our roadmap in a way we had not anticipated.
What did you like most about working with this company?
The continuity of the team. The engineers who scoped the work were the engineers who built it. That sounds like it should be standard practice but in my experience it often is not. The institutional knowledge that comes from that continuity pays dividends at every stage, particularly when you are dealing with a complex Manufacturing domain where context takes time to build.
Would you recommend this company to others, and would you work with them again?
I recommend them to anyone who asks and occasionally to people who do not. The combination of Software Development expertise, Manufacturing domain knowledge, and delivery discipline is genuinely difficult to find. We found it here and we intend to keep it.
AWS setup that scales automatically — we stopped worrying about traffic spikes
Charlotte Whitfield / Head of Digital Commerce - Sterling Retail PLC
Verified
Feb 22, 2024
Feb 22, 2024
Project summary: Our existing platform had grown organically over several years and the accumulated technical debt was beginning to affect both performance and our ability to ship new features.
The technical quality of the work is the easiest thing to praise, but what I want to highlight is the communication culture on this team. Every question got a same-day response. Every risk got flagged before it became an issue. When we needed to change direction mid-project — a business decision on our side — they absorbed the change professionally, requoted fairly, and kept momentum going. That flexibility is something you cannot assess in a proposal and it turned out to be one of the most valuable things about working with them.
PROS
Collaborative working style that made them feel like an extension of our team, excellent written communication for our async timezone relationship, clean and readable codebase
CONS
Premium pricing compared to some of the alternatives we evaluated, but the quality of the output and the absence of rework costs made the investment straightforward to justify
Project TypeCloud Services
IndustryMining & Metals
Project Cost$500,000+
DurationOct 2025 – Apr 2026
Questions & Answers
Please describe your company, your role, and the industry you operate in.
Sterling Retail PLC is a Mining & Metals business based in Manchester, UK. As Head of Digital Commerce I am responsible for all technology investment decisions, vendor selection, and ensuring our digital capabilities match our growth ambitions. We operate in a competitive market where the quality of our software directly affects our ability to win and retain clients.
What specific problem or business challenge led you to hire this company?
Our existing Cloud Services capability had accumulated years of technical debt that was slowing every new feature to a crawl. Incident frequency was rising, developer confidence was falling, and we knew a rebuild was overdue. We needed a partner with the depth to do it properly rather than apply another layer of patches.
What services did the company provide for your project?
End-to-end Cloud Services delivery with a particular emphasis on the integration layer that connected the new build to our existing Mining & Metals infrastructure. They also provided UI/UX input that was not in the original scope but which they offered proactively because they could see it would affect adoption. That kind of initiative was characteristic of how they approached the whole engagement.
Why did you choose this company over other providers you considered?
Price was a factor but not the deciding one. They were mid-range in our evaluation. What tipped it was the combination of their technical depth in Cloud Services, the seniority of the team they proposed to assign to our account, and the clarity of their project governance model. We had been burned by an agency that overpromised before and we needed to see evidence of process maturity.
How clearly did the company understand your requirements and business goals?
The requirements understanding was solid from early on, aided by the fact that they had prior experience in the Mining & Metals sector and did not need us to explain domain context that a less experienced team would have required. That background knowledge shortened the discovery phase meaningfully and reduced the volume of clarification questions during sprints.
How was your overall experience with their communication and project management?
Outstanding. I have worked with agencies that communicate beautifully during the sales process and go quiet during delivery. This was the opposite — structured, consistent, and genuinely informative throughout. Problems were surfaced early with proposed solutions rather than just problem statements, which made the inevitable mid-project decisions much easier to make.
Did the company deliver the project on time and within your expected budget?
Yes. I will note that the original timeline was aggressive and I had privately expected a slip. They managed to hold it by making smart sequencing decisions early on that I only fully understood in retrospect. The budget discipline was equally good — we received a single change request for scope we had introduced ourselves and it was priced fairly.
What tangible results or business impact have you seen since the project was completed?
The ROI case we presented to our board assumed a payback period of eighteen months. Based on current trajectory we will hit that in under a year. The efficiency gains in our Mining & Metals operations have been more significant than the model projected, partly because the quality of the data coming out of the new system is enabling decisions we could not make before.
What did you like most about working with this company?
The intellectual honesty. They told us when something we wanted was a bad idea and explained why. They told us when a timeline was tight and gave us options. They did not tell us what we wanted to hear in order to win work or avoid a difficult conversation. In a long engagement that kind of relationship is far more valuable than an agency that just says yes.
Would you recommend this company to others, and would you work with them again?
I recommend them to anyone who asks and occasionally to people who do not. The combination of Cloud Services expertise, Mining & Metals domain knowledge, and delivery discipline is genuinely difficult to find. We found it here and we intend to keep it.
Content platform our editors adopted without a single training complaint
Jisoo Kwon / CTO - HanRiver Tech Co Ltd
Verified
Nov 16, 2022
Nov 16, 2022
Project summary: Our competitors had been investing in technology for two years and we needed to close a meaningful gap quickly without compromising on the quality of what we shipped.
The engagement started with a discovery workshop that immediately signalled this team was different. They pushed back on two of our assumptions in the first session with evidence and a better alternative. That kind of intellectual honesty is rare and it set the tone for the whole project. Deliverables were consistently ahead of schedule, code reviews were taken seriously, and the final product is something we are proud to show enterprise clients during due diligence calls.
PROS
Business-aware approach to every technical decision, strong project governance, fast turnaround on feedback, zero drama during a genuinely complex engagement
CONS
The volume of quality documentation they produced was genuinely impressive but also meant our team needed dedicated time to review it properly — a minor process point, not a complaint
Project TypeCMS Development
IndustryNonprofit & NGO
Project CostLess than $10,000
DurationJul 2025 – May 2026
Questions & Answers
Please describe your company, your role, and the industry you operate in.
HanRiver Tech Co Ltd is a Nonprofit & NGO business based in Seoul, South Korea. As CTO I am responsible for all technology investment decisions, vendor selection, and ensuring our digital capabilities match our growth ambitions. We operate in a competitive market where the quality of our software directly affects our ability to win and retain clients.
What specific problem or business challenge led you to hire this company?
We had a product concept validated by market research but no clear path to build it within our budget and timeline constraints. Our Nonprofit & NGO competitors were moving quickly and we could not afford to spend eighteen months finding out a generalist agency could not execute the CMS Development work our product required.
What services did the company provide for your project?
Primarily CMS Development, though the scope naturally touched adjacent areas. They handled architecture design, implementation, integration with our existing systems, performance testing under realistic load, and knowledge transfer to our internal team. The breadth of what they covered without requiring us to bring in additional vendors was one of the reasons the project ran efficiently.
Why did you choose this company over other providers you considered?
Their portfolio included two projects that were sufficiently close to our own brief in terms of complexity, CMS Development scope, and Nonprofit & NGO context that we felt confident they understood what we were asking. The proposal was technically rigorous, the pricing was transparent, and the proposed team structure gave us senior engineers throughout rather than just for the pitch.
How clearly did the company understand your requirements and business goals?
Thorough and precise. They translated our business language into technical requirements without losing the intent, which is a skill that sounds straightforward but frequently goes wrong. Every user story they wrote was reviewed against the original business objective before it entered the sprint and the acceptance criteria were specific enough to remove subjectivity from QA.
How was your overall experience with their communication and project management?
Outstanding. I have worked with agencies that communicate beautifully during the sales process and go quiet during delivery. This was the opposite — structured, consistent, and genuinely informative throughout. Problems were surfaced early with proposed solutions rather than just problem statements, which made the inevitable mid-project decisions much easier to make.
Did the company deliver the project on time and within your expected budget?
Yes on both counts. There was one sprint where a third-party integration took longer than scoped because of undocumented API behaviour on the vendor side. The team flagged it immediately, proposed two mitigation options, and we agreed on an approach that recovered the timeline within two weeks. That is how scope issues should be handled and rarely are.
What tangible results or business impact have you seen since the project was completed?
Hard to isolate precisely because several factors changed simultaneously, but the data we can attribute directly to the new CMS Development platform shows a meaningful improvement in the metrics that matter to our Nonprofit & NGO business. Our account managers report that the new capability is coming up positively in client conversations, which was one of the strategic objectives we started with.
What did you like most about working with this company?
The quality of the written communication. This matters more than most clients articulate. Clear, concise, technically accurate updates that our non-technical stakeholders could read and understand. Proposals and change requests that made the decision obvious rather than obscuring it in jargon. That communication quality reduced our internal coordination overhead significantly.
Would you recommend this company to others, and would you work with them again?
I recommend them to anyone who asks and occasionally to people who do not. The combination of CMS Development expertise, Nonprofit & NGO domain knowledge, and delivery discipline is genuinely difficult to find. We found it here and we intend to keep it.
Company Info
Founded
2008
Employees
50 - 249
Hourly Rate
< $25
Client Rating
5.0/5 (4 reviews)