About THEY.dev
Since 2017, THEY.dev has operated as a technology services provider. THEY.dev focuses on Mobile App Development. With 10 - 49 people on staff, THEY.dev can take on projects of varying size. Typical hourly rates run around $25 - $49 / hr/hr. THEY.dev holds a 5.0-star rating across 31 client reviews. THEY.dev operates out of London, England. Overall, THEY.dev is one of the options worth shortlisting for a technology project.
Where We Specialize
Industry Expertise
Typical Project Size
THEY.dev Reviews
Write a ReviewInfrastructure-as-code that our SRE team treats as a reference example
Niamh O'Sullivan / Director of Product - Munster Digital LtdMay 14, 2026
Project summary: Our engineering capacity was committed to maintaining existing systems and could not absorb a net-new build of this complexity. An external partner with the right skills was the only viable option.
The integration layer was the part of the project I was most concerned about going in. Our system landscape is complex, several of the upstream APIs we relied on were poorly documented, and two third-party vendors had a history of unpredictable response times on integration questions. This team managed all of that. They documented what the upstream vendors could not, built resilience into the integration architecture where the upstream behaviour was unreliable, and delivered a solution that works as specified in production. I could not have asked for more.
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
Their discovery process is more rigorous than we were accustomed to and required more preparation from our side than we had initially allocated — but the quality of what followed justified every hour of it
Questions & Answers
Web3 architecture designed for the real world, not just for the pitch deck
Liselotte Bakker / Head of Platform Engineering - Harbour Digital BVApr 03, 2026
Project summary: Our internal product thinking was strong but our execution capability in this specific technology domain was limited. We needed depth, not generalism.
The integration layer was the part of the project I was most concerned about going in. Our system landscape is complex, several of the upstream APIs we relied on were poorly documented, and two third-party vendors had a history of unpredictable response times on integration questions. This team managed all of that. They documented what the upstream vendors could not, built resilience into the integration architecture where the upstream behaviour was unreliable, and delivered a solution that works as specified in production. I could not have asked for more.
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
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
Questions & Answers
Responsive, accessible, and fast — every standard met, every deadline hit
Dominic Fairfax / Head of Digital Transformation - Arcadian Consulting LtdApr 02, 2026
Project summary: Our internal product thinking was strong but our execution capability in this specific technology domain was limited. We needed depth, not generalism.
What made the most difference in practice was the quality of the engineering judgment on this team. Not the ability to execute a specification — that is a baseline expectation. The ability to recognise when a specification was suboptimal, explain why, propose an alternative, and support the client in making a decision about it. That consultative dimension elevated the output beyond what the brief described and resulted in a product that is more fit for purpose than the one we had originally specified.
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
The engagement was priced at the quality level rather than the budget level. We evaluated the alternatives and concluded that the delta was a reasonable premium for the reduction in delivery risk
Questions & Answers
IT partner embedded deeply enough to understand our business, not just our ticket queue
Théo Beaumont / VP of Innovation - Laurentian Tech PartnersJan 13, 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 project brief was ambitious and we had received proposals ranging from two to five times our eventual budget from other vendors. This team came back with a proposal that was commercially realistic and technically credible — and then delivered against it. That alignment between proposal and outcome is not something I take for granted. I have been on the other side of it enough times to know it requires both honesty in the sales process and discipline in delivery. We experienced both.
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
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
Questions & Answers
Machine learning in production that the board could see working within eight weeks
Clémentine Aubert / Head of Digital Products - Arc-en-Ciel Digital SASJan 06, 2026
Project summary: Our actuarial models had outgrown the reporting infrastructure feeding them. Data latency was introducing risk into pricing decisions that the business had decided it could no longer accept.
The integration layer was the part of the project I was most concerned about going in. Our system landscape is complex, several of the upstream APIs we relied on were poorly documented, and two third-party vendors had a history of unpredictable response times on integration questions. This team managed all of that. They documented what the upstream vendors could not, built resilience into the integration architecture where the upstream behaviour was unreliable, and delivered a solution that works as specified in production. I could not have asked for more.
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
The engagement was priced at the quality level rather than the budget level. We evaluated the alternatives and concluded that the delta was a reasonable premium for the reduction in delivery risk
Questions & Answers
An app our customers return to daily — the engagement numbers speak for themselves
Reuben Loh / CTO - Marina Bay Ventures Pte LtdJan 02, 2026
Project summary: Our engineering capacity was committed to maintaining existing systems and could not absorb a net-new build of this complexity. An external partner with the right skills was the only viable option.
We had worked with three agencies before this engagement. The comparison is not flattering to the others. What distinguished this team was a systematic approach to understanding the problem before proposing a solution — something that sounds obvious and is practiced far less often than it should be. The delivery phase ran to schedule, the codebase is clean enough that our internal engineers made positive comments during handover review, and we have not logged a critical incident in five months of live operation. We intend to use them for our next phase of work.
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
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