Concept21

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4.3/5 (23 reviews)
+48531313339 karol@concept21.agency Visit Website

About Concept21

Since 2015, Concept21 has operated as a technology services provider. Concept21 focuses on Web Development. Concept21 employs 10 - 49 people. Projects are generally billed around $50 - $99 / hr/hr. Concept21 holds a 4.7-star rating across 9 client reviews. This gives a quick snapshot of what to expect when working with Concept21.

Where We Specialize

24% Mobile App Development
Mobile App Development 24%
Platform Development 18%
Virtual Reality 16%
VR App Development 15%
AI Development 12%
Enterprise App Modernization 8%
Game Development 7%

Industry Expertise

Retail100%

Typical Project Size

48% Small Business
40% Enterprise
12% Midmarket Business

Concept21 Reviews

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An app our customers return to daily — the engagement numbers speak for themselves

Tobias Lindemann / Leiter Digitalisierung - Lindemann Industrie GmbH
Verified
Feb 14, 2026

Project summary: Several years of incremental development had left us with a platform that was technically functional but strategically limiting. A structured rebuild was the agreed path forward.

Six months after go-live our platform is processing three times the transaction volume we specified in the original brief. The architecture choices made during discovery accommodated that growth without remediation work. That is the difference between a team that designs for what you tell them and a team that designs for what you are likely to need. We are in conversation about a Phase 2 engagement and I expect to be using this partnership for several years.

PROS

Production system that has performed as specified since go-live without remediation work, documentation thorough enough to support internal maintenance, knowledge transfer that left our team genuinely capable

CONS

Time zone coordination required some deliberate overlap management from both sides in the first couple of sprints, after which we had an efficient async rhythm that worked for the whole project

4.5
Overall
5.0
Quality
4.0
Schedule
4.5
Cost
4.5
Communication
Project TypeMobile App Development
IndustryFood & Beverage
Project Cost$500,000+
DurationSep 2025 – Dec 2025

Questions & Answers

Please describe your company, your role, and the industry you operate in.
As Leiter Digitalisierung at Lindemann Industrie GmbH I oversee technology investment and delivery across our Food & Beverage operations in Berlin, Germany. We are a commercially focused business and our technology choices are always evaluated in terms of their direct contribution to business outcomes rather than technical elegance alone.
What specific problem or business challenge led you to hire this company?
A competitive threat had accelerated our roadmap. We had planned a significant Mobile App Development investment for the following year. External pressure moved that timeline forward by six months and required us to find an external partner rather than attempting to build internally in the time available.
What services did the company provide for your project?
End-to-end Mobile App Development delivery with particular depth in the integration and data migration components, which were the highest-risk elements of the programme. They supplemented this with a dedicated QA resource throughout development and a documented runbook for our operations team at handover.
Why did you choose this company over other providers you considered?
A trusted peer in the Food & Beverage sector had used them for a comparable Mobile App Development engagement and their recommendation was unequivocal. Our own due diligence confirmed the pattern they described. The combination of domain knowledge, Mobile App Development depth, and demonstrated delivery discipline was the deciding factor.
How clearly did the company understand your requirements and business goals?
Thoroughly and precisely. The requirements document they produced was detailed enough that our QA team used it directly to write acceptance criteria. Every user story had a defined business objective attached. Nothing was left to interpretation. That discipline in the requirements phase paid dividends throughout development and testing.
How was your overall experience with their communication and project management?
The project management framework was the most structured I have experienced with an external vendor. Sprint planning was tight, acceptance criteria were specific, retrospectives were honest and acted on. The project manager treated the shared backlog as a live document and the risk register as an operational tool rather than a compliance artefact. I never had to ask for a status update.
Did the company deliver the project on time and within your expected budget?
The project landed on time. The budget was managed within the agreed ceiling, which included one client-driven scope addition that was quoted fairly and handled without affecting the original delivery stream. The discipline around budget transparency throughout meant there was no surprise at invoice stage.
What tangible results or business impact have you seen since the project was completed?
The most direct measure is the performance of the system in production. In the five months since go-live we have had zero P1 incidents, our page performance scores have improved across every Core Web Vitals metric, and two enterprise clients who had cited our previous platform limitations during contract negotiations have since renewed without that objection arising.
What did you like most about working with this company?
The post-launch behaviour. Some vendors consider go-live to be the end of their professional obligation. This team treated it as the transition to a different kind of engagement. The hypercare period was substantive, the documentation was thorough and genuinely useful, and they checked in proactively at the thirty-day and ninety-day marks to review production metrics with us.
Would you recommend this company to others, and would you work with them again?
Unreservedly. We are in active scoping conversations for a second engagement and I expect this to develop into a multi-year partnership. For any organisation in the Food & Beverage sector looking for Mobile App Development expertise combined with genuine delivery discipline, I would put this team at the top of the evaluation list.

An app our customers return to daily — the engagement numbers speak for themselves

Kelsey Drummond / Director of Digital Health - Crestline Health Partners
Verified
Feb 10, 2026

Project summary: Grid modernisation funding required us to demonstrate demand-response capability. The machine learning models existed on paper; we needed an engineering partner to build and productionise them.

We gave this team an aggressive timeline, a technically complex scope, and a client-side project team that was stretched thin and not always available at the speed the engagement required. They absorbed all of that gracefully. Where they needed input they were precise about what they needed and when. Where they could proceed independently they did. The result was a delivery that landed on time despite the constraints on our side, which I regard as evidence of genuine professional maturity.

PROS

Senior-level engineering presence throughout the entire project, not just during the pitch, honest and commercially fair handling of scope changes, codebase that our internal team praised on review

CONS

We underestimated the input required from our subject matter experts during the requirements phase. The team flagged this early but our resource planning did not fully reflect it — our responsibility, not theirs

4.5
Overall
4.5
Quality
4.0
Schedule
4.5
Cost
4.5
Communication
Project TypeMobile App Development
IndustryEnergy & Utilities
Project Cost$10,000 to $49,999
DurationSep 2025 – Dec 2025

Questions & Answers

Please describe your company, your role, and the industry you operate in.
Crestline Health Partners is an established Energy & Utilities organisation headquartered in Houston, USA. My role as Director of Digital Health covers both strategic planning and operational technology delivery. We maintain high standards for our vendors because our clients hold us to high standards — a bar we expect our partners to meet.
What specific problem or business challenge led you to hire this company?
A competitive threat had accelerated our roadmap. We had planned a significant Mobile App Development investment for the following year. External pressure moved that timeline forward by six months and required us to find an external partner rather than attempting to build internally in the time available.
What services did the company provide for your project?
The scope covered the full Mobile App Development lifecycle: discovery and requirements definition, solution architecture, iterative development across twelve sprints, integration testing, performance validation, production deployment, and a structured four-week hypercare period. They also provided system documentation and a knowledge transfer programme for our internal team.
Why did you choose this company over other providers you considered?
A trusted peer in the Energy & Utilities sector had used them for a comparable Mobile App Development engagement and their recommendation was unequivocal. Our own due diligence confirmed the pattern they described. The combination of domain knowledge, Mobile App Development depth, and demonstrated delivery discipline was the deciding factor.
How clearly did the company understand your requirements and business goals?
Extremely well, in part because they had relevant Energy & Utilities experience that reduced the context-setting overhead significantly. They understood the domain vocabulary, asked the right questions, and translated business requirements into technical specifications with a fidelity that meant the development phase had very few clarification cycles.
How was your overall experience with their communication and project management?
Outstanding. The discipline around asynchronous communication was particularly effective given the time zones involved between Houston, USA and the delivery team. Written updates were specific and consistent, response times were same-day for anything that required a decision, and nothing fell through the cracks across a six-month engagement.
Did the company deliver the project on time and within your expected budget?
Yes. I had privately built a contingency expectation into my planning given the project complexity and the number of integrations involved. None of that contingency was needed. The delivery landed on the agreed date and the final invoice matched the approved budget to within a fraction of a percent. That outcome is rarer than the industry acknowledges.
What tangible results or business impact have you seen since the project was completed?
The ROI case we presented to our board was conservative by design. Current performance against the financial model suggests we will hit the projected payback point in under twelve months against an eighteen-month target. The operational efficiency gains in particular have exceeded the model, in part because the quality of the data the new platform generates supports decisions that the previous system could not.
What did you like most about working with this company?
The willingness to be direct. When our requirements were unclear they said so. When our priorities were contradictory they explained why. When a technical approach we had assumed was the right one turned out to have significant downsides, they told us before we had committed to it. That kind of intellectual honesty is what I look for in a long-term technology partner.
Would you recommend this company to others, and would you work with them again?
Yes. I would add the context that this is not the cheapest option in the market and they are selective about the engagements they take on. If your primary criterion is price, there are alternatives. If you want a technology partner who can be trusted with a complex Mobile App Development programme in the Energy & Utilities space and will deliver against a serious brief, this is the team.

SEO work that moved our primary keywords from page two to position three in five months

Zofia Kamińska / CTO - Odra Tech Studio
Verified
Jan 23, 2026

Project summary: The project had a board-facing delivery date tied to a strategic initiative. We needed a partner who would treat that date as their own, not ours.

The thing that retrospectively seems most significant is how little drama there was. Complex technology projects tend to accumulate incidents, escalations, and tense conversations. This one did not. Problems were surfaced before they became incidents. Scope changes were handled with process rather than conflict. Risks were managed rather than avoided. That level of maturity is rare in my experience and it made the delivery feel almost effortless from our side, which I know it was not from theirs.

PROS

Architectural decisions designed for longevity rather than just the current brief, thorough automated test coverage, post-launch stability that validated every technical choice made during discovery

CONS

The quality of documentation they produce means our team needed to set aside dedicated review time to do it justice — a minor scheduling point rather than a genuine criticism

4.5
Overall
4.5
Quality
5.0
Schedule
4.0
Cost
4.5
Communication
Project TypeDigital Marketing
IndustryNonprofit & NGO
Project Cost$500,000+
DurationMay 2025 – Nov 2025

Questions & Answers

Please describe your company, your role, and the industry you operate in.
I lead technology at Odra Tech Studio, a growth-stage Nonprofit & NGO business based in Wrocław, Poland. As CTO my remit spans product engineering, platform operations, and strategic vendor partnerships. We had reached an inflection point where our internal capacity was not sufficient to execute our roadmap at the pace our market required.
What specific problem or business challenge led you to hire this company?
We had a defined product vision for our next phase of growth in the Nonprofit & NGO market but lacked the engineering depth internally to execute it. The Digital Marketing requirements in particular required specialist experience that we could not realistically recruit for on the timeline our business plan required.
What services did the company provide for your project?
The core engagement was Digital Marketing delivery, though their scope expanded to include technical consultancy during discovery that materially improved our requirements. They also took ownership of the third-party integration workstream that had been a coordination challenge in previous projects, removing that complexity from our internal team entirely.
Why did you choose this company over other providers you considered?
The quality of the questions they asked during the briefing process was the first indicator. Vendors who ask precise questions in the sales phase tend to apply the same rigour during delivery. That hypothesis proved accurate. The technical proposal was substantive, the team structure was senior throughout, and the pricing was transparent.
How clearly did the company understand your requirements and business goals?
Thoroughly and precisely. The requirements document they produced was detailed enough that our QA team used it directly to write acceptance criteria. Every user story had a defined business objective attached. Nothing was left to interpretation. That discipline in the requirements phase paid dividends throughout development and testing.
How was your overall experience with their communication and project management?
The project management framework was the most structured I have experienced with an external vendor. Sprint planning was tight, acceptance criteria were specific, retrospectives were honest and acted on. The project manager treated the shared backlog as a live document and the risk register as an operational tool rather than a compliance artefact. I never had to ask for a status update.
Did the company deliver the project on time and within your expected budget?
On time and within the approved budget. The estimation accuracy was notable — they had broken the work down in sufficient detail during discovery that their forecast proved reliable throughout, rather than being a number that shifted with every change in scope. We received one change request and it was for scope we had introduced ourselves.
What tangible results or business impact have you seen since the project was completed?
The most direct measure is the performance of the system in production. In the five months since go-live we have had zero P1 incidents, our page performance scores have improved across every Core Web Vitals metric, and two enterprise clients who had cited our previous platform limitations during contract negotiations have since renewed without that objection arising.
What did you like most about working with this company?
The continuity of the team. The engineers who participated in the discovery sessions were the engineers who built the system. That consistency of institutional knowledge across a six-month project has a value that is difficult to quantify but easy to notice when it is absent. Every conversation built on the previous ones.
Would you recommend this company to others, and would you work with them again?
Absolutely. With a specific note that the value starts in the discovery phase — clients who approach that process with seriousness will get the most from the engagement. We invested appropriately at the front end and the returns are evident in what was delivered.

Company Info

Founded 2015
Employees 10 - 49
Hourly Rate $50 - $99 / hr
Client Rating 4.3/5 (23 reviews)

Rating Breakdown

Quality
4.3
Schedule
4.2
Cost
4.3
Communication
4.4