Fystack

Fystack is an open-source, self-hostable custody platform that gives fintech companies, payment processors, and digital-asset businesses the infrastructure to manage stablecoin wallets across more than ten blockchains — including Solana — without relying on a centralized custodian or building their own key management system from scratch.

The core problem Fystack addresses is the steep cost and complexity of enterprise-grade crypto custody. Companies that want to accept or route stablecoin payments typically face a choice between paying volume-based fees to custodians such as Fireblocks or Cobo, or spending six or more months and significant engineering resources building proprietary wallet infrastructure. Fystack offers a third path: a production-ready, open-core stack that can be deployed on a company's own infrastructure in days, with flat licensing rather than per-transaction cuts eating into margins.

How it works

The technical foundation is Multi-Party Computation (MPC) implemented through a distributed cluster Fystack calls MPCIUM. MPCIUM is built on Binance's tss-lib threshold-signing library. The key property of threshold signing is that no single server ever holds an assembled private key; instead, key material is split across multiple MPC nodes, and a signing quorum must cooperate to authorize any transaction. Keys at rest are protected using a DEK/KEK hybrid encryption model, and Fystack's documentation describes additional runtime memory encryption and data-tampering detection controls. Integration with external Key Management Services — AWS KMS and Google Cloud KMS — is supported for organizations with existing secrets infrastructure.

Four services make up the Fystack runtime: Apex, the backend API that handles wallet management, user authentication, transaction policies, and audit trails; MPCIUM, the distributed signing cluster; a Multichain Indexer that tracks on-chain deposits in real time across supported networks; and a Rescanner service that fills in any block gaps the indexer may miss. The backing data layer uses PostgreSQL, Redis, MongoDB, and NATS messaging with Consul for service discovery.

Products and features

The Apex API exposes endpoints for wallet creation and management, asset transfers, payment checkout flows, webhooks, policy enforcement, and workspace administration. Developers interact with it through a REST interface with SDK support. From the operator side, a unified dashboard provides multi-chain wallet visibility, real-time monitoring, and alert routing to Telegram or Slack.

Auto-sweep is one of the more operationally significant features: it automatically aggregates incoming deposits from generated deposit addresses into consolidation wallets, removing the manual reconciliation work common in payment operations. A transaction policy engine allows teams to define spending limits, whitelist approved destination addresses, and require multi-party approvals before large transfers are executed. Role-based access control (RBAC) and complete audit trails with integrity signing support regulatory reporting requirements.

Deployment is flexible. Fystack can run as a cloud SaaS offering for teams that want a managed environment, but the primary positioning is self-hosted: Docker Compose for quick-start testing, Kubernetes for production scale, or bare metal. A Cosigners feature — independent hardware-based co-signers providing an additional approval layer — is listed as upcoming in the product roadmap.

Supported assets and chains

Fystack supports more than 100 tokens across more than ten blockchains. The current live networks include Bitcoin, Ethereum, Solana, Tron, BNB Smart Chain, and Base, with Stellar listed as coming soon. The primary assets in focus are USDT and USDC, reflecting the stablecoin payment use case, though the 100-token figure suggests broad coverage of liquid assets across the supported chains. Solana is explicitly highlighted in Fystack's content as a preferred chain for stablecoin flows due to its low transaction fees and settlement speed.

Security and audit

On June 23, 2026, Adevar Labs — a security firm whose team includes veterans from Bitdefender, Quantstamp, and Chainproof — completed a full audit of the Apex backend. The scope covered authentication and session handling, payment processing workflows, wallet signing and MPC message handling, webhook delivery systems, and the database and CI/CD deployment pipeline. The audit found one Critical issue (hardcoded sandbox credentials), nine High findings, 29 Medium findings, and 23 Low findings. The sole Critical finding was promptly remediated and independently re-validated by Adevar Labs. Six of nine High findings were fixed; three were acknowledged with documented reasoning. Fystack published the complete audit report rather than issuing only a badge, allowing prospective customers to review findings and remediation status directly. Notable hardening actions included enforcing fail-closed security behaviors, patching webhook validation against DNS rebinding attacks, strengthening cryptographic configuration, and aligning transaction signing with RFC 8785 standards.

Team and traction

Fystack was founded in July 2025. As of mid-2026 the company reports more than 20 self-hosted instances running in production. Named customers and ecosystem participants include ApeScreener, Gaian, EXDT, Minepath, PrimePay, and Superteam. The self-host scripts repository on GitHub is licensed under Apache-2.0, and the project's open-core positioning — where the self-hosted deployment scripts are public but enterprise configurations require direct engagement — reflects a model common among developer-infrastructure companies targeting regulated industries.

Fit in the Solana ecosystem

Fystack's relevance to Solana sits at the infrastructure layer rather than the DeFi or consumer product layer. By providing MPC custody and payment rails that include Solana as a first-class supported chain, Fystack enables fintech companies and payment processors to build stablecoin products on Solana without managing raw keypairs or relying on hosted custody services. The platform's emphasis on Solana in its content — including dedicated blog posts on Solana's emerging role in global payments and a comparison of Ethereum versus Solana for enterprise stablecoin adoption — indicates active investment in the Solana use case. For Solana-based projects seeking a compliance-ready, self-hosted custody layer for treasury automation or payment product development, Fystack provides a deployable option backed by a completed security audit.