Blockchain Development

Custom blockchain development: what it is and what it includes

Custom blockchain development is the design, coding, testing and deployment of software on a blockchain network for a specific use case: the smart contracts, the tokens, the application people use and the integrations with the systems the company already has. It also covers decisions you do not see in the code: which network to use, who controls each function, what gets audited before production and who maintains the system afterward.

It makes sense when several independent organizations write to the same record and none of them accepts another one owning the server, or when an asset has to move between identified people under rules that are checked on every transfer. If a single organization owns the data, a database with an immutable audit trail is cheaper to run, and we will tell you so before we quote.

Custom does not mean starting from scratch: we build on reviewed standards and libraries and write only the logic that is specific to your business. If you want a platform under your own brand without a long development cycle, compare it with our white-label tokenization platform.

What we build

• Smart contracts. Business logic in Solidity smart contracts for EVM networks, such as coupon payments, redemptions or votes. If a contract depends on outside data, such as a price, the oracle that supplies it is selected and secured as part of the contract.
• Tokens. Token development to fit the case: ERC-20 for interchangeable units, ERC-721 for unique items, ERC-1155 for several series in a single contract and ERC-3643 for instruments that only identified investors may hold.
• Decentralized applications. The interface and backend on top of the contracts: dApp development.
• Tokenization platforms. Investor portal, issuer dashboard, identity registry and transfer rules: tokenization platform development.
• Wallets and custody. Multisig or MPC, amount-based approvals and rehearsed recovery: crypto wallet and custody development.
• Integrations. With the KYC/AML provider, the custodian, the registry entity, the intermediary and the client's ERP, plus collecting payments in tokens pegged to the euro or the dollar: stablecoin payment integration.
• Private blockchains. Permissioned networks for consortiums: private blockchains, for example a traceability system where the manufacturer, carrier and distributor record milestones for the same batch.

Technologies and networks

Ethereum and EVM-compatible networks

We build on the Ethereum Virtual Machine (EVM), the execution environment shared by Ethereum and networks such as Polygon, Arbitrum, Base, Optimism, Avalanche and BNB Chain. The same contract can be deployed on several of them with the same tools. The network determines the cost per transaction, the time until a transaction becomes irreversible and the risk of moving funds between chains:

Language, tools and libraries

We write contracts in Solidity with Foundry (Solidity tests, fuzzing, invariants and gas measurement) and use Hardhat when TypeScript scripts are needed. For what is already solved and reviewed (role-based access control, emergency pause and ERC-20, ERC-721 and ERC-1155 implementations) we start from OpenZeppelin. Our own code is reserved for the business logic.

Every contract goes through unit tests, tests against a copy of the live network (a fork) and static analysis, and is verified on each network's block explorer. Technical details in Ethereum (EVM) development.

When a private network makes sense

If you need personal data on-chain or confidentiality between participants, a public network is not the answer: we propose a permissioned network or rule out blockchain altogether.

• Hyperledger Fabric, with X.509 identities, channels and private data collections, when confidentiality between subgroups is the priority and no token is wanted.
• Besu or GoQuorum, with a full EVM and privacy groups, when the team already works with Solidity tooling.
• A public network with contract-level permissions, when access lists and data encrypted off-chain are enough.

In a private network, trust shifts from cryptoeconomics to consortium governance, so its rules (who joins, how an upgrade is approved, what happens if a member leaves) are written before the first node goes up. More in public vs. private blockchain.

How we work: from idea to mainnet, phase by phase

1. Discovery and scope

We start from the problem: what gets recorded, who signs, who can change the rules and which systems we need to connect to. If there is a token, its legal nature is settled with the client's legal counsel before fixing supply and permissions, because the technical standard does not determine it; the MiCA or MiFID II classifier gives a first orientation. Once the scope is closed, the timeline can be estimated.

2. Architecture

We choose the network with cost and volume figures in hand and decide what goes on-chain and what stays off-chain; personal data stays off. We also set the system's governance: an upgradeable proxy or an immutable contract, privileged functions signed from a multisig and never from a single key, and sensitive changes behind a timelock.

3. Iterative delivery, with testnet testing

We work in releases that the client's team tests on a test network (testnet), where real operations are rehearsed before moving to production.

4. Audit before mainnet

We perform smart contract audits, with static analysis, manual review and a report that records each finding, its severity and the exact version reviewed. For systems that hold value, we recommend a review by someone other than the person who wrote the code, and for issuances with complex logic, such as vesting or restricted transfers, we add an independent external audit.

5. Deployment and maintenance

We deploy with versioned, reproducible scripts, not by hand from a console. At project close you receive:

• The repository with the contracts, tests and deployment scripts.
• The addresses and verified code on each network, with the hashes of the deployment transactions.
• The architecture document: roles, privileged functions and upgrade and pause procedures.
• Monitoring and alerts on critical functions, with the response runbook.

After that, a system with real users takes work every month (patches, keys, versioned changes), and that maintenance is budgeted from the start.

Use cases in Spain and their legal framework

For securities, crypto-assets or payments, the token's classification, the offering route and the entities that must be involved are set by the client's legal counsel; we build the technology that applies them.

Asset tokenization: Law 6/2023 and the ERIR

Law 6/2023 on Securities Markets and Investment Services allows transferable securities to be represented through systems based on distributed ledger technology (Art. 6(1)). The issuer prepares an issuance document (Art. 7) and, under Art. 8(4), designates in it the entity or entities responsible for administering the registration and recording of the securities in the system, the ERIR, which in all cases must be authorized for the safekeeping and administration of financial instruments on behalf of clients (Art. 126(a)). For securities that only identified investors may hold, we start from ERC-3643 and build the investor portal and the integration with the designated ERIR.

Crypto-assets: MiCA

If the token is not a financial instrument, it may be a crypto-asset subject to Regulation (EU) 2023/1114 (MiCA), which does not apply to crypto-assets that qualify as financial instruments (Art. 2(4)(a)). For a crypto-asset other than an asset-referenced token or an e-money token, offering it to the public requires, among other things, being a legal person and drawing up, notifying and publishing a crypto-asset white paper (Art. 4(1)), although Art. 4(2) and 4(3) exempt certain offers from all or part of those obligations. And providing crypto-asset services, such as holding clients' crypto-assets or their private keys in custody, requires being an authorized provider (CASP) or one of the eligible financial entities (Arts. 3(1)(16), 3(1)(17) and 59(1)), which shapes the design of a wallet from day one.

Stablecoin payments

MiCA defines an e-money token as a crypto-asset that aims to keep a stable value by referencing the value of one official currency (Art. 3(1)(7)). As a general rule, only its issuer, authorized as a credit institution or an electronic money institution and with a notified and published white paper, may offer it to the public or seek its admission to trading; other persons may do so only with the issuer's written consent (Art. 48(1)). A company that only accepts it as a means of payment is not its issuer, although if it converts, holds client balances or intermediates for others, the analysis changes. We build the payment collection, confirmation and ERP reconciliation layer.

Traceability

Beyond the product's sector rules, data protection matters: the right to erasure under Regulation (EU) 2016/679 (Art. 17) does not fit an immutable record, and its Art. 25 requires data protection by design. On-chain we keep the proof of integrity (the data hash and the signature of whoever recorded it), and personal data stays off.

How much blockchain development costs and how long it takes

We do not publish rates: two projects with the same contract can differ by an order of magnitude. What drives budget and timeline:

• Scope. Whether third-party money is involved, how many people sign and whether they must be able to operate without bringing their own wallet.
• Network. The cost per transaction has to match the expected volume; choosing a chain by reputation is a common way to overspend.
• Integrations. KYC/AML, custodian, ERIR, intermediaries and ERP; in wallets and payments, that layer is usually most of the development.
• Audit. Its scope, whether an external review is added and the new reviews if the code changes.
• Regulation and maintenance. The closer to regulated money, the more the upfront work weighs against the coding; and maintenance adds up every month.

The timeline can only be estimated once the scope is closed, and for an issuance the launch date also depends on the offering documents and the intermediaries. For securities, we break down the line items in how much it costs and how long it takes to issue a security token in Spain.

Frequently asked questions

What does a blockchain development company do?

It designs, codes, tests and deploys software on a blockchain network: smart contracts, tokens, applications and integrations. Much of the work comes before the code: deciding whether blockchain adds anything, choosing the network, setting who controls each function and planning the audit and maintenance.

Which blockchain should I choose for my project?

It depends on the amount of each transaction, the volume and who bears the trust. With many small end-user transactions, a layer 2 wins on cost; if the system settles large amounts or needs finality on Ethereum without intermediaries, mainnet justifies it. If there is confidential data among identified participants, the answer is usually a permissioned network.

What do I get at the end, and who controls the contracts?

The repository with contracts, tests and deployment scripts, the verified code on each network, the architecture document and the monitoring. For a token's contracts, ownership and the administrative roles are transferred to whoever you decide, and privileged functions sit behind a multisig.

Do smart contracts need an audit?

If the contract will hold value, yes, and before mainnet. An audit narrows the risk within a scope, a specific version and commit, but it does not certify the absence of bugs or cover later changes. That is why it is combined with tests, multisig, an emergency pause and monitoring.

Do you work with companies outside Spain?

Yes. We work from Málaga with clients in Spain, Switzerland and the United Arab Emirates, and we build platforms for issuers in the European Union, Latin America and the United States. Outside Spain we do so with the client's local legal counsel and, in the United States, with their securities lawyer and the registered intermediaries each offering requires.

Official sources

• Law 6/2023 of March 17 on Securities Markets and Investment Services (BOE, consolidated text, in Spanish)
• Regulation (EU) 2023/1114 on markets in crypto-assets (MiCA) (EUR-Lex)
• Regulation (EU) 2016/679, the General Data Protection Regulation (EUR-Lex)
• Ethereum standards (EIPs): ERC-20, ERC-721, ERC-1155 and ERC-3643 (T-REX)

Who we are

Unknown Gravity is a Spanish blockchain and tokenization technology company based in Málaga. We build and maintain smart contracts, platforms and integrations. We are not an investment firm, an ERIR, a crypto-asset service provider or a law firm: we work alongside the client's legal counsel and the regulated entities each project needs.

If you are comparing providers, see our ranking of blockchain development companies in Spain and Europe.

Framework verified as of October 14, 2026. Have a project in mind? Talk to us.