Kotlin Jobs in Web3

About Blackbird:

Blackbird Labs is a loyalty and payments platform establishing meaningful connections between the world’s best restaurants and their customers.

Served up in 2022 by Ben Leventhal, co-founder of Eater and Resy, Blackbird offers a fully customizable loyalty programming platform for restaurants and a consumer app designed to make every guest feel like a bonafide VIP no matter where they dine. Backed by Union Square Ventures, a16z, Amex Ventures, Variant Fund, and other forward-thinking investors, Blackbird is out to revolutionize the restaurant industry.

About Our Team:

At Blackbird, our values guide everything we do and our talent principles define the key traits we seek in our employees.

We have passion for our product – committed to our mission and instinctively think like and go the extra mile for our customers. We are elite performers – striving for excellence, going above and beyond to achieve exceptional results, and learning quickly with horsepower, drive, and grit. We make others better – taking initiative to elevate others, giving and receiving feedback, and championing a culture of growth. We hold one another accountable to living out our talent principles as we march together to achieving our mission.

We are an in-office culture that values the power of in-person connection and collaboration. Just as Blackbird fosters magical in-restaurant experiences, we believe being together ignites creativity, accelerates problem-solving, and strengthens the team spirit essential to driving our mission forward.

About the Job

At Blackbird, we believe every guest should feel like a VIP the moment they walk into a restaurant. Whether it’s last-minute tables, welcome drinks, off-menu items, or exclusive perks, we’re building a platform that helps restaurants identify, connect with, and reward their guests in meaningful and personalized ways.

Our vision? The more you check in at your favorite spots, the more you unlock—from unique rewards to seamless direct messaging for reservations. With each visit, you’ll earn $FLY, our universal rewards currency, which you can use across our network of outstanding restaurants.

As a Senior Backend Engineer, you’ll bridge traditional fintech and blockchain technologies to build our next-generation payments infrastructure. You’ll collaborate with product managers, designers, and fellow engineers to define and execute the technical vision behind our crypto payments and loyalty platforms. You’ll shape key architectural decisions, establish engineering best practices, and help scale secure, user-friendly Web3 payment experiences.

We’re looking for someone who thrives in a fast-paced, high-ownership environment and is passionate about building products that seamlessly bridge the on-chain and off-chain worlds.

Responsibilities

• Design, build, and maintain backend APIs that integrate blockchain transactions with traditional payment systems.

• Integrate on-chain wallet services, managing wallet lifecycle events, transactions, and user authentication.

• Implement secure and scalable solutions for on-chain payment flows, transaction signing, and state reconciliation.

• Work with smart contracts, blockchain oracles, and data providers to facilitate reliable on-chain interactions.

• Uphold and promote backend best practices with a focus on security, testing, and reliability.

• Mentor engineers and foster a collaborative, growth-oriented team culture.

• Participate in product and design discussions, providing backend and blockchain perspectives on implementation and feasibility.

Requirements

• 5+ years of experience building and deploying backend APIs.

• Strong proficiency in Kotlin or another statically typed JVM language.

• Working knowledge of Solidity, smart contract design, and EVM-based ecosystems.

• Experience designing RESTful APIs and distributed systems using domain-driven design principles.

• Familiarity with blockchain architectures, smart contract interactions, wallet authentication flows, and transaction signing.

• Strong attention to detail and commitment to delivering secure, high-quality user experiences.

• Comfortable working cross-functionally with product, design, and engineering teams.

Nice to Haves

• Experience with Spring Boot, Hibernate, and asynchronous event-driven architectures.

• Familiarity with the U.S. payments ecosystem, including debit, credit, and ACH processing.

• Exposure to AWS infrastructure, Terraform, and CI/CD pipelines.

• Understanding of cryptographic primitives (signatures, hashing, key management).

• Experience with embedded wallet SDKs (e.g., MetaMask, WalletConnect) or user identity systems (OAuth, Web3 login flows, Auth0).

• Experience building in-app crypto wallets or integrating on-chain/off-chain loyalty systems.
  

Pay Transparency Notice & Benefits

Depending on your work location and experience the target annual salary for this position can range from: $180,000-$220,000 USD. This range does not include the equity component of the overall compensation package. Disclosure in accordance with New York City's Pay Transparency Law.

Full time offers from Blackbird may also include stock options, benefits (including medical, dental, vision, flexible time off, 401(k)), and some not-so-standard, extra-fun perks — subject to applicable taxes and based on eligibility.

Commitment to Equal Opportunity

Blackbird Labs is committed to diversity in its workforce and is proud to be an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, creed, gender, national origin, age, disability, veteran status, sex, gender expression or identity, sexual orientation or any other basis protected by applicable law. Blackbird will also consider for employment qualified applicants with criminal histories in a manner consistent with applicable law. For US applicants, you may view the Know Your Rights notice here. Additionally, Blackbird participates in the E-Verify program.

Join us and find out what the best work of your career could look like here at Blackbird.