Backend Engineer

Overview

We are looking for a Senior Engineer to take primary ownership of its Go-based Virtual Signer and help maintain shared signing SDKs and integrations across server and mobile platforms.
 

The Virtual Signer participates in MPC and threshold signing alongside mobile devices. This is an opportunity to take ownership of a security-critical component, strengthen its production reliability, and contribute to future transaction approval and post-quantum signature capabilities.

About the Environment:
The Go-based Virtual Signer orchestrates signing between server and mobile participants. It integrates with MPC and threshold-signature libraries, supports encrypted storage and must recover safely from interrupted signing sessions and other failures.

The component has been rebuilt over roughly the past year and is around MVP stage. It is working, with outstanding pull requests, logging and visibility improvements, and race conditions to address. The incoming engineer may have limited handover from the previous maintainer.

The engineer will work with backend and mobile engineers, testing support and a cryptographer who also maintains the repository. Collaboration across UK and Eastern Canada working hours will be important.

The environment includes Go, Linux and Docker, with shared SDKs and bindings for Swift, Kotlin and JavaScript/TypeScript. Jira, Slack, GitHub and Google Workspace are used for collaboration.

The initial focus is a robust production baseline: understand the codebase, resolve reliability and security issues, improve tests and support releases. Later work may include transaction approval functionality and post-quantum signing in collaboration with cryptography specialists.

Responsibilities:
Virtual Signer Engineering
— Maintain and improve the Go Virtual Signer, including signing orchestration, communication between participants, encrypted storage and recovery from failures.
— Investigate concurrency, timeouts, interrupted sessions, network failures and service restarts; review outstanding pull requests and address race conditions.
— Improve logging and visibility, assess the existing implementation critically and make careful, maintainable changes.
— Support agreed transaction approval features and future post-quantum signature work.
 

Cryptography, SDKs & Cross-Platform Integration
— Maintain integrations with MPC and threshold-signature libraries, working with cryptography specialists where changes affect protocol security.
— Contribute to shared SDKs and bindings connecting Go with Swift, Kotlin and JavaScript/TypeScript.
— Work with backend and mobile engineers to preserve API compatibility and consistent signing behaviour across releases.
 

Quality, Testing & Operations
— Improve automated tests for signing correctness, failure recovery and interoperability between virtual and mobile signers.
— Support Linux and Docker deployments, dependency upgrades, monitoring, release processes and operational documentation.
— Investigate production issues and occasionally assist with customer setup or logging problems.

Ownership & Technical Judgement
— Take primary ownership of a security-critical codebase with limited handover and independently establish a robust production baseline.
— Assess technical risks and trade-offs, explain decisions clearly and make incremental changes with sound security judgement.
— Collaborate pragmatically with backend, mobile, testing and cryptography specialists across time zone

Requirements:
Essential Technical Experience
— Strong hands-on production Go, including goroutines, channels, context cancellation, race detection, profiling and resource management.
— Experience owning production services, diagnosing complex failures and delivering well-tested fixes.
— Distributed-systems knowledge, including asynchronous messaging, retries, idempotency, state management and partial failures.
— Practical security engineering: authentication, encrypted storage, sensitive-data handling and safe logging.
— Applied cryptography concepts, including digital signatures, hashing, key management and signature verification.
— Automated testing, CI/CD, Linux, containers and production observability.
— Ability to understand an established codebase, make careful incremental changes and explain technical decisions clearly.

Strongly Preferred/Desirable Technical Experience
— JavaScript/TypeScript SDKs and mobile bindings, including asynchronous APIs, packaging, compatibility and Go/mobile interoperation.
— React Native/Expo, Swift or Kotlin; experience with mobile lifecycle, secure storage or native modules.
— MPC or threshold signatures, distributed key generation and changes to signing participants.
— Blockchain transaction signing, including signing payloads and chain-specific requirements.
— Confidential computing and hardware attestation, particularly AMD SEV-SNP, are especially valuable among the desirable skills.
— MQTT, Protocol Buffers, Prometheus or OpenTelemetry; familiarity with post-quantum signature schemes is also desirable for the longer-term roadmap.
 

Market Experience
— Experience with digital asset infrastructure, blockchain signing or MPC is valuable, but the priority is strong production Go and sound security judgement.
— Relevant experience in other security-critical distributed systems can also demonstrate fit.
— Candidates do not need experience with every desirable technology; evidence of ownership, careful delivery and learning across platform boundaries matters.

Soft Skills 
— Independent and able to understand an existing repository with limited handover.
— Strong security judgement, attention to correctness and a careful approach to critical signing systems.
— Able to assess implementation choices critically and explain risks and trade-offs clearly.
— Pragmatic and collaborative when working with backend, mobile and cryptography specialists.
— Comfortable diagnosing production failures and improving reliability through tested changes.
— Effective remote communication and flexibility for collaboration across UK and Eastern Canada working hours.
— Able to take ownership without relying on detailed instructions or extensive handover.
— Willing to investigate occasional customer setup or logging issues.

Assessment Process
Stage 1: CV screening.
Stage 2: First-stage technical interview (30 mins).
Stage 3: Technical Interview (1 hour) including pair-programming.
Stage 4: Cultural alignment review (30 mins).