Blockchain
Cryptocurrency
The engineering behind crypto payments and wallets — built by people who take irreversible mistakes seriously.
Overview
Cryptocurrency, from an engineering standpoint, is a set of systems for moving and holding value on public blockchains: accepting crypto payments in a product, generating and securing wallets, signing and broadcasting transactions, tracking what settled on-chain, and reconciling all of it against your own ledger. It has almost nothing to do with the trading, speculation, and price commentary that dominate the headlines. We build the software plumbing — the part where a customer pays in a stablecoin, a wallet is created for them, a transaction is signed with a key that must never leak, and your accounts show the right number the next morning.
What makes this domain different from ordinary payments engineering is that mistakes are final. There is no chargeback, no reversal, and no support line at the blockchain. Send funds to the wrong address and they are gone. Lose the private key that controls a wallet and the assets it holds are gone. Let an attacker sign one transaction and they can drain everything that key controls. That single property — irreversibility — reshapes every decision, which is why the discipline here is overwhelmingly about key management, signing controls, and defence in depth rather than about clever features.
Yarqat builds compliant, secure crypto-integrated software for businesses with a genuine operational need — a payment rail, a settlement flow, a product that must custody or move digital assets. We are engineers, not advisers: we do not run a fund, we do not tell anyone what to buy or hold, and we do not predict prices. We are also honest that a great many businesses exploring crypto do not actually need it, and we will say so before you spend money. Where crypto genuinely fits, the value we add is the security and regulatory discipline that this space punishes you for skipping.
Best for — Businesses with a genuine, specific need to accept or move cryptocurrency as part of their product — where the engineering priority is security, compliance, and correct reconciliation, not speculation.
Why teams choose Cryptocurrency
Security treated as the whole job
In this domain a single leaked key ends the business, so we design key management, signing controls, and cold/hot separation first and build features around them — the inverse of how most software is written, and the only sane order here.
Compliance built in, not bolted on
KYC/AML checks, transaction monitoring hooks, audit trails, and record-keeping are designed into the system from the start, so that when a bank, auditor, or the FCA asks how your flows work, the answer already exists in the code and the logs.
Operational settlement that survives volatility
For most payment use cases we convert to fiat immediately at the point of sale, so your books are denominated in pounds and your margins are not hostage to a price swing between checkout and settlement.
Why businesses choose Cryptocurrency
- You need crypto engineering done by people who treat key management and irreversibility with the seriousness the domain demands, not as an afterthought bolted onto a normal web app.
- You want compliance and security designed in from the first commit, because you understand that retrofitting them after a problem is far more expensive than building them in.
- You want an honest partner who will tell you if you do not actually need crypto, and who refuses to build speculative or advice-giving features that create financial and legal risk.
- You value senior engineers who will make conservative, defensible choices — audited libraries, established custody patterns, hardware-backed signing — over whatever novel protocol is fashionable this quarter.
What we build with Cryptocurrency
The capabilities this technology is genuinely strong at — and what we most often build with it.
Wallet generation and HD key derivation
We build wallet systems using hierarchical deterministic (BIP-32/39/44) derivation, so a single securely-stored seed produces a tree of addresses without exposing the master secret. We are precise about where seeds are generated, how they are backed up, and who can ever reconstruct them.
Custodial vs non-custodial architecture
The single biggest design decision is who holds the keys. Custodial systems mean you hold customer funds — maximum control, maximum liability, and a regulatory obligation. Non-custodial means users hold their own keys — far less risk for you, but a different product. We help you choose deliberately and build accordingly.
Hot and cold wallet separation
We keep only the minimum float in hot wallets connected to signing infrastructure, with the bulk of assets in cold storage that is never online. Movement between the two is a controlled, monitored, thresholded operation — because the hot wallet is the part attackers will try hardest to reach.
HSM and hardware-backed signing
Where custody warrants it, private keys live inside a hardware security module or equivalent, and transactions are signed there without the key ever entering application memory. This turns a leaked server into a bounded incident rather than a total loss.
On-chain transaction handling and reconciliation
We build the unglamorous core: constructing transactions, estimating fees, broadcasting, waiting for the right number of confirmations, handling reorgs and stuck transactions, and reconciling every on-chain event against your internal ledger so your books and the blockchain never silently diverge.
Payment-processor and exchange integration
Rather than reinvent custody where it is not core, we integrate established processors and exchange APIs for acceptance, off-ramping, and immediate fiat settlement — with idempotent handling, webhook verification, and reconciliation so a dropped callback never loses or double-counts a payment.
Use cases
Crypto payment acceptance with fiat settlement
A product that lets customers pay in crypto or stablecoins, converts to fiat at the point of sale through an integrated processor, and settles clean pounds to your account — removing volatility from your books while offering the payment method your customers asked for.
Stablecoin cross-border settlement
Moving value between entities or countries using stablecoins where correspondent banking is slow or costly, with the compliance checks, monitoring, and reconciliation needed to satisfy your banking partners and auditors.
In-product wallet infrastructure
Wallets embedded in a platform — for payouts, balances, or internal transfers — built on HD derivation with a clear custodial model, controlled signing, and cold-storage discipline for anything beyond an operational float.
On-chain reconciliation and treasury tooling
Software that watches addresses, ingests confirmed transactions, matches them to invoices or expected flows, and surfaces discrepancies — the operational backbone that keeps a crypto-handling business auditable and solvent.
When Cryptocurrency is the right choice
- You have a concrete, demonstrated need to accept or settle payments in cryptocurrency — customers who genuinely want to pay that way, cross-border flows where it removes real friction, or a stablecoin settlement leg — rather than a vague sense that you should be in crypto.
- You are building a product that must custody or move digital assets as a core function, and you accept that this brings a serious, ongoing security and compliance obligation that you are prepared to fund properly.
- You operate in, or are willing to enter, a regulated posture: you understand that KYC/AML, licensing, and jurisdiction-specific rules apply, and you would rather build compliantly from day one than retrofit it after a regulator or bank asks questions.
- Wrong for: businesses reaching for crypto as a marketing signal or because competitors mention it. If you cannot name the specific problem crypto solves that a conventional payment processor does not, you almost certainly do not need it, and we will tell you so.
- Wrong for: anyone wanting a system that treats crypto as a speculative position — holding assets for appreciation, timing markets, or offering trading. That is not engineering we do, it carries financial and regulatory risk we will not take on, and most businesses that think they want it actually want boring, reliable settlement to fiat.
Cryptocurrency: pros and cons
Strengths
- Blockchain settlement is final and cryptographically verifiable — once confirmed, a payment cannot be quietly reversed, which removes chargeback fraud from the equation.
- Cross-border value transfer can be faster and cheaper than correspondent banking, particularly with stablecoins, which is the one use case where the benefit is often real and measurable.
- On-chain transactions are publicly auditable, so reconciliation and proof of payment can be built on a shared, tamper-evident source of truth rather than a private ledger nobody outside can verify.
- Programmable payments and stablecoins let you build settlement logic — escrow, conditional release, automated payouts — directly into the transaction layer where it belongs.
Trade-offs
- Transactions are irreversible and errors are catastrophic: a wrong address, a bug in an amount calculation, or a stolen key means permanent, unrecoverable loss with no support desk to call.
- The regulatory burden is heavy and shifting — KYC/AML obligations, registration and licensing regimes such as the FCA’s in the UK, and rules that differ by jurisdiction and change without much notice — and getting it wrong risks enforcement, frozen banking, and personal liability.
- Price volatility makes crypto held on the balance sheet operationally painful; most businesses must settle to fiat immediately, which adds an exchange integration and its own counterparty and timing risk.
- The space is a magnet for fraud, scams, and money laundering, so crypto-adjacency carries reputational risk and heightened scrutiny from banks and payment partners even when your own conduct is impeccable.
Architecture
The architecture of a crypto system is organised around one question: where do private keys live, and what is allowed to make them sign. We draw a hard boundary between the parts of the system that touch keys and everything else. Signing sits in an isolated, minimal service — ideally backed by an HSM — that accepts a narrow set of validated instructions and returns signatures, and never exposes raw key material to the application layer that faces the internet. The web tier, the API, and the business logic can be compromised without the attacker gaining the ability to move funds, because they were never trusted with that ability in the first place.
Around that core we build the ordinary but essential machinery: a node connection or a reputable node provider for reading chain state and broadcasting, a confirmation-tracking service that understands reorgs and finality, an internal double-entry ledger that is the system of record for balances, and a reconciliation loop that continually checks the ledger against on-chain reality. Cold storage lives entirely outside this online system, with movements into the hot float requiring multiple approvals. Compliance components — identity checks, screening, and monitoring — sit in the transaction path, not off to the side, so a payment cannot complete without passing them.
Performance
Performance in crypto systems is rarely about raw throughput in your own code and mostly about the chain and the integrations around it. Confirmation times are set by the network, not by you, so the engineering task is designing flows that behave correctly while a transaction is pending — clear pending states, sensible confirmation thresholds tuned to the value at stake, and idempotent handling so a user refreshing or a webhook retrying never double-spends or double-credits.
Where we do optimise is in not hammering nodes, batching reads, caching chain state that does not change, and handling fee estimation well so transactions confirm in a reasonable window without overpaying. We treat node providers and exchange APIs as unreliable dependencies — they rate-limit, lag, and occasionally return stale data — and build retries, circuit breakers, and reconciliation that assume any single call might fail. The goal is a system that stays correct and calm under network congestion, not one that pretends the blockchain is fast.
Security
This is the part of a crypto build that matters more than everything else combined, because the consequence of failure is not downtime or embarrassment but permanent, irreversible loss. Cryptocurrency systems are among the most targeted software on the internet: attackers are financially motivated, well-resourced, and only need to succeed once. We design accordingly. Private keys are generated in secure environments, never logged, never transmitted, and where custody warrants it never leave a hardware security module. Signing is gated behind strict validation, spending limits, and — for material amounts — multiple approvals, so no single compromised component or person can move funds.
Beyond keys, we assume the perimeter will be breached and limit the blast radius: minimal hot-wallet floats, cold storage offline, least-privilege access everywhere, and thorough audit logging of every signing request and fund movement. Address handling is treated as safety-critical — validation, checksums, and confirmation steps guard against the irreversible cost of a wrong destination. We favour audited, well-established libraries and custody patterns over novel cryptography, and we are candid that security here is a permanent operational commitment, not a one-time hardening pass. If you are not prepared to fund that commitment, you are not ready to hold crypto.
Scalability
Scaling a crypto system is less about serving more users and more about handling more value and more transactions without weakening the controls that keep funds safe. As volume grows, the hot-wallet float, the number of signing operations, and the reconciliation workload all increase, and each is a place where a shortcut taken for speed can become an exploitable weakness. We plan for growth by keeping the security architecture constant as throughput rises — the signing boundary, cold-storage discipline, and approval thresholds do not relax because you got busy.
Operationally, the components that scale are the readers and reconcilers: watching more addresses, ingesting more confirmed transactions, and matching them against a growing ledger. These are ordinary data-engineering problems and we treat them as such — horizontally scalable services, a database that can carry the ledger, and monitoring that alerts on divergence early. Multi-chain and multi-asset support adds breadth rather than depth, and we add it deliberately, because each new chain is new attack surface, new fee mechanics, and new failure modes to understand before, not after, it holds real money.
Cryptocurrency integrations & ecosystem
The technologies we most often pair with it — each links to how we work with it.
How we work
We start with a blunt conversation about whether you need crypto at all, and if you do, exactly which flows require it. Then we settle the decisions that are expensive to change later: the custodial model, where keys live, the compliance posture, and how settlement to fiat works. These are made before we write feature code, because in this domain the security and regulatory architecture is the product, and everything else hangs off it.
From there we build in thin, real slices — a single payment flow end to end, with its signing, reconciliation, and compliance checks in place — rather than a broad prototype that ignores the hard parts. The engineers who design the custody and signing model are the ones who write and operate it, so the people making irreversible decisions are the ones who will live with them. We favour audited libraries, established custody patterns, and conservative choices, and we document the security model so your team and your auditors can understand exactly how funds are protected.
The service behind it
Delivered throughBlockchain DevelopmentWhat we build with Cryptocurrency
The disciplines this technology most often shows up in — from a first build to taking over and stabilising an existing one.
How we deliver
- 01
Discover
We map the system, the constraints and the business it serves — including the parts nobody documented.
Architecture brief
- 02
Architect
Decisions get made, written down and defended before a line of production code exists.
Decision records
- 03
Build
Short cycles against working software. You see progress in the product, not in a status deck.
Shipping increments
- 04
Operate
Monitoring, incident response and iteration. The system is alive, so the engagement is too.
Runbooks & SLOs
Industries we use Cryptocurrency in
Domain knowledge changes what gets built. A few of the sectors we know before the first meeting.
Also in Blockchain
Why teams choose us for Cryptocurrency
We take irreversibility seriously
This domain punishes carelessness with permanent loss, so we design key management and signing controls first and treat security as the whole job, not a hardening pass at the end. That discipline is the difference between a crypto system that survives and one that makes the news.
Compliance-first, honestly
We build KYC/AML, monitoring, and record-keeping into the system from the start, and we are candid that requirements vary by jurisdiction and change. We will not build you something that looks compliant today and collapses under a regulator’s question tomorrow.
Engineering only — no financial advice
We build software. We do not run funds, recommend assets, predict prices, or offer investment advice of any kind. That boundary keeps us focused on doing the engineering exceptionally well and keeps you clear of risk we have no business taking on.
Honest about whether you need it
Many businesses exploring crypto do not actually need it, and a conventional payment processor would serve them better. We would rather tell you that and lose the project than build you a liability you did not require.
Typical timeline
- 01
Discovery and risk assessment
One to two weeks establishing whether crypto is genuinely needed, the custodial model, the regulatory obligations that apply, and the threat model — the decisions that shape everything after.
- 02
Security and compliance architecture
Designing key management, signing boundaries, cold/hot separation, and the KYC/AML and monitoring flows before feature work begins, so security is the foundation rather than a later addition.
- 03
First payment or wallet flow
Building one real flow end to end — signing, confirmation handling, reconciliation, and compliance checks included — to prove the architecture against the actual chain rather than a plan.
- 04
Hardening and handover
Independent review of key handling and signing controls, reconciliation testing against edge cases, audit logging, and documentation so your team can operate the system safely.
How pricing works
- A discovery and design engagement to settle the custodial model, compliance requirements, and security architecture — often the most valuable phase, and sometimes the one where we conclude you do not need crypto at all.
- Fixed-scope builds for well-defined integrations — crypto payment acceptance with fiat settlement, or a specific wallet or reconciliation system — quoted once the security and compliance requirements are clear.
- Monthly senior engagement for ongoing crypto product work, where the flows evolve and you need continuity from people who already understand your key-management and compliance model.
- Security-focused reviews of existing crypto systems — key handling, signing controls, and reconciliation — priced by the assessment.
Hire Cryptocurrency engineers
Need Cryptocurrency capacity on your own team? We embed named senior engineers into your existing team — reporting to your leads, working in your rituals — so you add capacity without a hiring cycle.
Hire Cryptocurrency engineersCommon questions
Do you provide investment or financial advice on cryptocurrency?
No. We are a software engineering consultancy and nothing more. We do not give investment or financial advice, we do not recommend buying, selling, or holding any cryptocurrency or token, and we do not make price predictions. What we do is build secure, compliant software that integrates crypto payments, wallets, and on-chain handling for businesses with a genuine operational need. If you want advice on assets or markets, we are not the right people — speak to a regulated financial adviser.
Custodial or non-custodial — which should we build?
It depends entirely on your product and your appetite for risk and regulation. Custodial means you hold customer keys and funds: more control, but you take on serious liability and a regulatory obligation. Non-custodial means users hold their own keys: far less risk for you, but a different product and user experience. This is the most consequential decision in the build, and we settle it deliberately with you up front rather than letting it be decided by accident.
How do you handle the volatility of crypto payments?
For most payment use cases, we convert to fiat immediately at the point of sale through an integrated processor or exchange, so your books stay denominated in pounds and a price swing between checkout and settlement never touches your margins. Holding crypto on the balance sheet is a deliberate treasury decision with real operational and accounting consequences, and it is not something we would build without you understanding exactly what it involves.
What happens about KYC, AML, and licensing?
We build the technical hooks for identity verification, screening, transaction monitoring, and record-keeping into the system from the start, and we design flows so a payment cannot complete without passing the required checks. What we cannot do is tell you your precise legal obligations — those depend on your jurisdiction, your activities, and rules that change, including FCA registration requirements in the UK. You will need qualified legal and compliance advice, and we build to satisfy it.
What is the real risk of losing funds, and how do you guard against it?
The risk is permanent, irreversible loss — from a leaked private key, a signed malicious transaction, or funds sent to a wrong address, none of which can be reversed. We guard against it with layered defences: keys generated securely and, where warranted, kept inside hardware security modules; strict signing controls, spending limits, and multi-approval for material amounts; minimal hot-wallet floats with the bulk in offline cold storage; and safety-critical address validation. Security in this domain is a permanent operational commitment, not a one-time task, and we are honest that it must be funded as such.
Building on Cryptocurrency?
A technical conversation with the engineers who would do the work. If we are not the right fit, we will say so on the call.