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Built with Stellar Community FundSoroban Scan is live on mainnet!Built for the Soroban era - smart contracts, payments, NFTs, liquidity pools, all decoded.Try it now!
Soroban Scan dashboard showing live Stellar network stats and the latest transactions

Who we are

Hi there! We're Rumble Fish - a team of world-class experts in bespoke software development. Our engineers are highly skilled in blockchain, cloud solutions, and defi/fintech development. Our strength and pride is the ability to take ownership of the entire development process and be a true partner and advisor for our customers. Our mission is to craft state-of-the-art digital products using battle-tested technologies. Try us!

MarekMarcinSylwiaKarolina

Meet the team

The engineers, strategists, and problem-solvers behind every Rumble Fish project.

Meet the team →
40uniquely skilled devs
1pet-friendly office
9years in business
57projects
999passion for coding

What do we do?

Software Development Services and Skills for your needs To deliver the highest quality of services, our experts are always gaining new skills and knowledge. That’s how we make sure our solutions follow the latest industry standards and take advantage of the most innovative technologies.

Our team is well-versed and experienced in various blockchain development tools and technologies. Our unique skillset allows us to be at the forefront of Web3 development services so if you’re looking for a trusted IT partner to boost your decentralized product - look no further!

We deliver production-ready zero-knowledge proof solutions that actually ship to mainnet, specializing in custom ZK development, rollup scaling solutions, and privacy-preserving smart contracts that reduce processing times from hours to minutes. Try us!

We build fast, compliant, and cost-effective blockchain solutions on the XRP Ledger. From payment systems and tokenization platforms to enterprise DeFi applications, our team delivers production-ready systems that work when billions are on the line.

Rumble Fish builds Stellar and Soroban software for startups, enterprises, and institutions. We develop payment rails, tokenization platforms, smart contracts, and DeFi applications that draw on Stellar's speed, low costs, and financial infrastructure.

We build smart contracts that handle real business complexity without the usual blockchain headaches. From DeFi protocols to custom on-chain systems, we deliver production-ready solutions that scale.

Decentralized Finance (DeFi) development requires an extensive amount of blockchain knowledge, as well as a great understanding of financial mechanisms. We’ve got both that bases covered! Our team has successfully built an impressive number of DeFi products like cryptocurrency exchanges, dApps, lending protocols, or staking platforms. Try us!

Our experienced team will take your AWS cloud solutions to the next level. AWS provides purpose-built tools to support your needs, and it is the preferred choice for any blockchain project. From the plethora of cloud tools and solutions offered by Amazon Web Services, we’ll help you choose and implement the ones that serve your business the best way possible.

AI chatbots can bring value to a wide range of industries by enhancing customer interactions, streamlining processes, and improving overall efficiency. We'll craft a perfect AI assistant for your product.

Need realistic data for AI training, testing, or product development—but privacy, scale, or availability is blocking you? We engineer custom synthetic data solutions that capture the complexity of real-world data without the constraints. From multi-modal generation to domain-specific datasets, we build what platforms can't deliver.

We build custom AI knowledge management systems that turn your scattered enterprise knowledge into instant, accurate answers - no more employees wasting their valuable time hunting through SharePoint and Slack for information. Unlike platforms that trap you in subscriptions, we engineer RAG solutions specifically for your data and security requirements, then hand you complete ownership of the source code and infrastructure.

Looking for a skilled team to help you build an advanced fintech platform able to compete with the biggest in the game? At Rumble Fish, we’ve got what it takes to engineer innovative financial technology systems. We offer end-to-end fintech software development, consulting, and expertise.

Our experts provide you with knowledge, skills, and experience that elevates every project to another level. We’ll gladly take ownership of the entire process and guide you and your team through the intricacies of cutting-edge technology development.

If you’re in need of professional web development services, look no further! Rumble Fish's talented team has extensive experience in delivering top-tier web apps and websites with the use of battle-tested tools and technologies like React or Nest. We know just the right solutions to exceed your business requirements.

Whether you need an Android, an IOS app, or both, the Rumble Fish team is here to help you deliver the beautiful and efficient mobile product that your customers will simply love to use! We craft fast and secure mobile apps with a wow factor to help our customers grow their businesses and reach their goals quicker.

If you're looking for a team capable of turning your product concept into a beautiful and technologically intricate digital solution - look no further! Rumble Fish is your trusted software development partner ready to take you through the entire process of custom digital product creation - from the early stages of ideation to the post-launch support. Whether you're on a mission to build a mobile app, a Web3 product, or an advanced platform - we are here for you!

We design sleek, intuitive, and highly effective interfaces to help you overcome your business challenges. After carefully evaluating and understanding your requirements we switch to the designing mode - the end goal is the beautiful digital solution that people love to use!

Don't take our word for it

“Rumble Fish was an exceptional development partner for the Afffirmations mobile app, demonstrating professionalism, technical expertise, and collaborative problem-solving. We highly recommend them for your next digital project
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Nicholas RevilleCofounder & CEO, Wonderful Wonderful
“We have been greatly satisfied with the services provided by Rumble Fish. Their team is friendly, knowledgeable, creative, and committed to helping us create a complex, blockchain-based royalty payment system. We are very thankful for their dedication and hard work.
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Alain PrasquierCTO at Revelator
“Our cooperation with Rumble Fish was easy and smooth. The team was able to provide us with a perfect solution and it was a great experience working with them.
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Sarah MasonCMO of Death Charades
“The developers at Rumble Fish Software Development are professional and capable of producing the highest quality code. I can recommend them with no doubt.
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Ari KardasisFounder and CTO of The Ocean
“Fantastic team! Rumble Fish offers world class technical solutions with personality and soul. It’s a client-based industry, everything is person to person. Guys have nailed it!
Alexander Mathiesen - Ohman_TestimonialAvatar
Alexander Mathiesen - OhmanFounder and CEO of The Solar Generation

Latest case study

Porting Merkl to Stellar: Full Protocol Migration to Soroban
Porting Merkl to Stellar: Full Protocol Migration to Soroban
Merkl is the leading onchain incentive infrastructure, having distributed over $1.6B in rewards for 250+ companies across 60+ chains.
Collaboration timeframe:4 weeks
Services:Smart Contract Development, Blockchain Development, Stellar Product Development, DeFi Development
Rumblefish Blog
Check a piece of expert knowledge
x402 on Stellar: Rumble Fish Receives Its Third Stellar Community Fund Grant_BlogPostImagex402 on Stellar: Rumble Fish Receives Its Third Stellar Community Fund Grant
375165173_10223182974989698_6377842045490346765_n.jpg_BlogPostAuthorAvatarBy Agnieszka Dobosz
**Rumble Fish has been awarded a grant from the Stellar Community Fund (SCF #45) to build x402 on Stellar: an open-source payment facilitator and Bazaar discovery layer that lets AI agents find, price, and pay for API endpoints and MCP tools on a per-request basis, in USDC or any SEP-41 asset.** This is our third SCF award this year. It follows the SCF #41 grant for the Soroban-first Block Explorer, [now live as Soroban Scan,](https://sorobanscan.rumblefish.dev/) and the SCF #42 grant for the [Stellar Prices API.](https://www.rumblefish.dev/blog/post/rumble-fish-grant-stellar-prices-API/) This time we were selected in the RFP Track (Developer Tooling), as one of three teams funded under the x402 Facilitator with Bazaar RFP. You can read the full round results in the [SCF #45 Round Recap.](https://medium.com/stellar-community/scf-45-round-recap-1ecf281821ab?postPublishedType=initial) ## Why AI Agents Need a Different Payment Model The way we pay for APIs today was designed for humans. You sign up, enter a card, pick a monthly plan, and copy an API key into your config. An AI agent that needs one price quote or one contract lookup can't fill in a signup form, and a $49 monthly subscription for a single call makes no sense for either side. x402 fixes this by reviving the long-dormant HTTP 402 "Payment Required" status code. When an agent calls a paid endpoint, the server responds with payment terms. The agent signs a payment, a facilitator verifies and settles it on-chain, and the request goes through. Payment becomes part of the HTTP request itself, with no accounts or keys involved. Stellar is a natural home for this pattern. Settlement costs around 0.0023 XLM per transaction, a fraction of a cent, which makes sub-cent pricing per request economically viable in a way it isn't on most other networks. ## What We're Building for x402 on Stellar The project has four main parts. The facilitator implements the x402 v2 verify, settle, and supported endpoints, accepts any SEP-41 token, and sponsors network fees so payers don't need to hold XLM. The Bazaar is a discovery catalog with ranked search based on relevance, quality score, and curation, so agents can find paid services by describing what they need. An MCP-native discovery server exposes search and paid calls as tools, which means agent runtimes can discover and pay for services without custom integration code. And SDKs in TypeScript and Rust cover both buyers and sellers. The Rust seller crate will be the first seller-side Rust integration in the x402 ecosystem. We're also adding a usage-based "upto" settlement scheme. The standard exact-price model breaks down for metered services, where the final cost depends on how many rows a query returns or how many tokens a model generates. With upto, the client authorizes a ceiling, and the server settles the actual amount used, never more. A Soroban proxy contract enforces the ceiling, expiry, and single-use nonces on-chain. We're submitting the scheme specification to the x402 Technical Steering Committee so it can become part of the protocol for every network, not only Stellar. Delivery happens in three tranches: a testnet foundation, a feature-complete release with the facilitator on pubnet and an external security audit underway, and a mainnet launch with audit findings resolved, a public conformance report listing settled mainnet transaction hashes, and a developer guide published to the Stellar Developer Docs. ## Real Services Instead of Demo Endpoints The RFP requires example integrations. We could have built a few synthetic endpoints that return hardcoded JSON, and they would pass every test. They would also tell us very little about how the infrastructure behaves under real use. So we're gating our own production services behind x402 instead. Soroban Scan and the Prices API will both accept x402 payments through the new Rust crate, alongside a canonical Express/TypeScript reference example. Real queries from real users hit edge cases that demo endpoints never will, and the facilitator gets production traffic from day one. It also gives both projects a sustainable monetization path that doesn't depend on grant funding. ## What the Team Says Marek Kowalski, CEO/CTO of Rumble Fish, sees this grant as the point where the team's earlier Stellar work comes together: #### "Agents are becoming real consumers of APIs, and they need to pay for what they use without a human filling in forms. Stellar has the fees and the settlement speed to make per-request payments work. We already run production services on Stellar, so we're building this as a team that will use it every day, not as a demo." ## What This Means for the Stellar Ecosystem Agentic payments are one of the fastest-moving areas in the industry right now, and the networks that offer the best developer experience for them will attract the services agents end up paying for. A facilitator, a discovery layer, MCP support, and SDKs in two languages give Stellar a complete stack for AI agent payments, available as open source for any team to run or build on. For us, this completes a line of infrastructure work: an explorer that makes Soroban readable, a price API that makes asset data consistent, and now a payment layer that makes both of them, and any other Stellar service, accessible to autonomous agents. You can track the project's progress on the [Stellar Community Fund.](https://communityfund.stellar.org/project/rumble-fish-software-development-rfp-6z9) If you're building on Stellar and need a technical partner who knows the ecosystem inside out, our team is ready to help, so [get in touch.](https://www.rumblefish.dev/contact/)
Blockchain
Modular Blockchain Architecture for Enterprise: The Decision You Can't Undo Later_BlogPostImageModular Blockchain Architecture for Enterprise: The Decision You Can't Undo Later
Most enterprise blockchain projects start with the wrong question. The first technical conversation is usually about which chain to pick. Ethereum? Hyperledger Fabric? Stellar? That question is premature, and the fact that it comes first explains why so many of these systems get rewritten eighteen months after launch. The right question is: which parts of this system will change independently of each other, and does your architecture account for that? Modular blockchain architecture, where execution, consensus, data availability, and settlement are separate, independently replaceable layers, is not a theoretical framework anymore. Layer 2 networks now account for the vast majority of Ethereum ecosystem transaction volume, with total L2 transactions growing from 135.6 million in January 2024 to over 543 million in early 2026 and daily activity consistently eclipsing Ethereum mainnet [(source)](https://arxiv.org/html/2606.22206v1). Celestia runs as a standalone data availability layer. BlackRock launched its BUIDL tokenized money market fund on Ethereum in March 2024 and by 2026 had expanded it across six chains with over $2.4 billion in assets under management [(source)](https://www.altrady.com/blog/cryptocurrency/blackrock-buidl-tokenized-treasury-2026), one of the clearest signals that on-chain institutional finance infrastructure has moved past proof of concept. The modular stack is production infrastructure. For institutions, the question is no longer whether to go modular, but where to draw the boundaries and what each boundary costs you. ## Why Monolithic Architectures Fail at Institutional Scale A monolithic blockchain handles execution, consensus, and storage in a single system. This has one genuine advantage: simplicity. One system, one security model, one set of documentation. For an internal proof of concept or a bounded pilot, this is often the right call. **The problem surfaces when the system exits the pilot stage.** Take a settlement system for tokenized treasury bonds. At launch, it processes a few hundred transactions per day. Compliance requires address-level KYC, counterparty whitelisting, and an immutable audit log that satisfies MiFID II. Consensus needs to be deterministic and fast; no institution will accept probabilistic finality for regulated settlement. And two years from now, **the same system needs to handle ten times the volume,** integrate with an external custody provider, and potentially expose part of its state to a public chain for regulatory transparency. In a monolithic system, each change touches everything. A consensus upgrade may require re-auditing smart contracts. A change to the access model may conflict with settlement logic. Scaling one layer scales all of them. **In a modular system, those layers are isolated.** You can replace the execution layer without touching settlement. You can add private data availability without changing consensus. You can, and this matters specifically for institutions, audit and scale each layer on its own schedule. ## The Four Layers That Cannot Be One Decision A practical modular blockchain architecture for enterprise separates four distinct concerns. Each has different requirements and a different rate of change. **The execution layer** is where business logic lives: smart contracts, compliance rules, settlement calculations. This layer changes most frequently, because business requirements shift, regulations evolve, and bugs in logic need fixing. For institutions, the critical requirement is deterministic execution and the ability to formally verify contract behavior. Stellar's Soroban platform, with its WebAssembly-based execution model and constrained environment, has a meaningful advantage over the EVM here. The cost model is predictable, the execution is sandboxed, and the host environment enforces strict resource limits that reduce the surface area for unexpected behavior. That predictability matters when you're processing regulated financial instruments. **The consensus layer** determines how network nodes agree on system state. For financial institutions, the key variables are finality time and the trust model. Probabilistic finality is not acceptable in settlement systems: a transaction that might be reversed is not a transaction you can book against. Byzantine Fault Tolerant consensus with deterministic finality, as in the Stellar Consensus Protocol, achieves finality in seconds while giving you control over who participates as a validator. That last point is underrated. Institutional settlement networks are not open networks. The ability to define the validator set, rather than inherit a public one, is often a compliance requirement. **The data availability layer** answers where data is stored and who can read it. This is the layer that most frequently requires customization in institutional contexts. Public data availability - Ethereum, Celestia - gives you maximum transparency and censorship resistance. Private or selective data availability lets you satisfy GDPR requirements, maintain confidentiality between counterparties, and restrict access to sensitive transaction details. In practice, institutional systems often need a hybrid model: public commitments to data, with private access to transaction specifics. Designing this as a first-class layer, rather than bolting on encryption as an afterthought, is the difference between a system that scales and one that accumulates compliance workarounds. **The settlement layer** is where value transfer becomes final and irreversible. For tokenized assets, this is frequently a separate decision from execution. You can run business logic on a private chain and record final settlement on a public ledger. This pattern is increasingly common in institutional DeFi: private execution for confidentiality, public settlement for regulatory auditability. It only works cleanly if the architecture separates these concerns from the start. Separating execution from settlement in a system that was never designed to distinguish between them means starting over. ## Where Enterprise Projects Go Wrong The most common architectural mistake we see is treating platform selection as a substitute for architectural decisions. A team picks Hyperledger Fabric because it's "enterprise-grade," and then tries to fit their compliance, scalability, and interoperability requirements to the platform's capabilities. The result is a system that satisfies the requirements on day one but has no upgrade path. The second mistake is underestimating what "compliance layer" actually means. In financial systems, compliance is not a feature you add at the end. KYC, AML, whitelisting, audit trails, reporting - each of these affects how you design the execution layer, how you manage data access, and how you integrate with external systems. Teams that define compliance requirements after making architectural decisions almost always end up with workarounds that become technical debt. The third mistake, and probably the most expensive: designing for pilot volume instead of production volume. A monolithic system handling 500 transactions per day can look perfectly scalable. The problem appears at 500,000. **Modular architecture lets you scale execution independently of settlement and data availability,** but only if that separation is built in from the start. There is no clean path to adding it later. A concrete example: one of the DeFi protocol architectures we worked on initially treated data availability and execution as the same layer, because in the prototype they effectively were. When the protocol needed to add privacy-preserving transaction batching for institutional counterparties, the assumption that "execution state is available state" was everywhere in the codebase. The change that should have touched the data availability layer required changes across settlement logic, indexing, and the API surface. Three weeks of work that should have been three days. ## What This Means for Architects Making the Decision Now The practical implication of the modular approach is that platform selection becomes secondary to architectural model selection. Before you decide on Ethereum, Stellar, XRPL, or a private Fabric network, there are questions that determine which architecture makes sense at all. **What finality time does the system require?** If the system handles regulated settlement, probabilistic finality is disqualifying regardless of a platform's other strengths. **Who controls data access?** If compliance requires selective disclosure, transaction details visible only to authorized counterparties and regulators, you need a data availability layer that handles this natively, not through encryption bolted on top of a public ledger. **Which layers will change in three years?** If you don't know, design the separation between them such that changing one doesn't require rewriting the others. That's the point of the separation. **Do you need interoperability with a public chain?** Hybrid models with private execution and public settlement are increasingly common, but they require specific approaches to bridge design and key management that need to be considered at the architecture stage, not after. Institutional blockchain adoption is accelerating because the platforms have matured to the point where these questions have concrete answers. **That platform maturity does not substitute for architectural maturity.** A system built on modular principles, with clear separation between execution, consensus, data availability, and settlement, can be scaled, audited, and evolved. A system built on an "enterprise-grade platform" without that separation will eventually become a migration project. The teams we see doing this well make the modular decision before they make the platform decision. The teams doing it poorly pick the platform first and then spend the next two years working around what they locked in. --- _Rumble Fish builds financial infrastructure and blockchain systems for institutions and scale-ups. If you're designing architecture for tokenized assets, settlement systems, or compliance-heavy DeFi -_ [_get in touch_](https://rumblefish.dev/contact)_._
Blockchain
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