Return | REMOTE | Senior Ruby/Rails developer (remote within EU) | Full-time (or 4 days)

Return (https://return.energy) is hiring a software engineer who will work on platforms that accelerate the transition to carbon-free energy. Return’s main activity is building and operating industrial-size Battery Energy Storage Systems. Our operations are located in the Netherlands, Germany, Belgium, and Spain. You will be making a measurable (country-level) impact on the transition to renewable energy. Return recently raised €300M to support its growth.

While we employ over 100 people, Return’s technical team is still small (15 people). Our platform automates processes in energy storage, monitoring, market optimization, sales, project management, procurement, construction, and customer service.

During the first three years of operation, we laid the foundation for our platforms, and we are ready to scale up. This is why we are looking for an experienced software engineer.

You will be working on internal tools that support our business departments (origination, development, construction, operation, and general). Our tech stack is straightforward: Postgres, Ruby on Rails 8, Turbo, Stimulus, and Tailwind. We tend to keep meetings to a minimum in order to provide at least five hours of uninterrupted coding time per day. We practice code reviews and apply automated and manual testing. The platform is often deployed multiple times per day.

We’re very much open to remote work as long as you live in the EU. Our hiring process is swift but thorough: a 30-minute call to get acquainted and discuss financials, one or more technical interviews, and a paid visit to Amsterdam to meet the team.

The tech team members have co-founded several companies and have experience with remote development teams since 2008. They will personally help you through most of the recruiting process (there is no recruiter involved).

Apply here: https://jobs.polymer.co/return/39294 (EU residents ONLY)

Duolingo | Full-time | Multiple roles | $177K-$240K for NY roles | NY and London | Hybrid

Our mission is to develop the best education in the world and make it universally accessible. Our culture is eng-driven, friendly, and very data-driven thanks to our large userbase. Check out our blog to see what engineering at Duolingo can look like: https://blog.duolingo.com/hub/engineering/

Tech stack: (frontends) Swift/Kotlin/TypeScript, (backend) Python/Kotlin/Postgres/Dynamo, (infra) AWS/k8s/Terraform.

We're always hiring for engineers. A few roles below:

Senior Engineering Manager, Chess (NY) https://careers.duolingo.com/jobs/8385137002

Senior Android Engineer (NY) https://careers.duolingo.com/jobs/8217266002

Senior iOS Software Engineer (NY) https://careers.duolingo.com/jobs/8318257002

Engineering Director (London) https://careers.duolingo.com/jobs/8444624002

Senior Gameplay Programmer (London) https://careers.duolingo.com/jobs/8424809002

Base salary: $177-240K for the NY-based roles, unsure about the London-based roles.

Perks: free lunch, 2-week winter break + 20 days of flexible time off.

Littlebird.ai | Sr. AI SWE's + React/RN + Product Analyst | Global+remote | Full-time

Littlebird is your AI-powered personal operating system. We capture context from your daily life -- meetings, messages, browsing, notes -- and use it to help you remember everything, prioritize your day, and solve real problems. If you get excited about designing bleeding edge personal agents, persistent memory, or conversational inference...please see below!

Our team: includes multiple ex-founders + YC alums based in the US, EU and IST

Core stack: Python, Swift, React / RN, Postgres

Sr. / Staff AI Systems Engineer: https://jobs.gem.com/littlebird/am9icG9zdDrOmVuqR5Sy4TSPZbhE...

Applied AI Engineer: https://jobs.gem.com/littlebird/am9icG9zdDpftgr_F1AcbaNAqQWn...

Sr. React / RN Engineer: https://jobs.gem.com/littlebird/am9icG9zdDrfqJE9Qs--i1a3EQck...

Product Data Analyst: https://jobs.gem.com/littlebird/am9icG9zdDqi-y222tVeoibOKM3-...

To apply, click on the links above and send us a resume and any github or personal projects you are proud of.

Pushscroll | Full-Stack Mobile Engineer (KMP) | REMOTE (GMT-3 to GMT+4)

We make people do push-ups before opening addictive apps - verified through camera pose detection. Our goal is to replace doomscrolling with exercise.

500k+ downloads, bootstrapped and profitable, very quickly growing.

Looking for someone strong in Kotlin Multiplatform + Compose Multiplatform + Swift/SwiftUI who works independently, uses AI to ship fast, and can implement a pixel-perfect Figma design.

Bonus: Supabase, Amplitude, native Android/iOS knowledge (e.g., Screen Time).

Small team, work directly with founders, long-term role. We’ve got big plans to make Pushscroll the app of the year, and there are exciting challenges to get there.

Reach out: contact@pushscroll.com

Apple | Software Engineer - Developer Tools/LLDB | London, UK | ONSITE (3 days/week in office)

The LLDB team is hiring an engineer to work on the debugger, which is used internally across Apple and externally by millions of developers. You'll drive features and improvements in LLDB, collaborating across teams working on the OS and toolchain. Responsibilities range from supporting new hardware and platforms to developing debugging features, with most work open-source (llvm.org & swift.org).

If you're passionate about developer tools with experience in system-level programming and knowledge of compiler/debugger/OS internals, we'd love to hear from you!

https://jobs.apple.com/en-gb/details/200643284/debugger-engi...

SpruceID (YC W21) | REMOTE (US-Based Preferred) | Full-Time | spruceid.com

Spruce lets users control their data across the web. Instead of users logging into platforms, we believe platforms should request to access data vaults controlled by users.

The demand for trusted digital ID is accelerating as AI deepfakes begin to destroy most of the ways we use to verify identity today. How private or secure is it to hold your driver's license or passport up to a webcam to get a bank account? Was it ever private or secure? Stable diffusion can break so much of this already. Society will need trusted digital IDs and credentials. Our mission is to allow them to be controlled by individuals, with safeguards to prevent descents into surveillance states and checkpoint societies.

We are the main implementers of category-defining initiatives such as the digital ID program for the California DMV, and the verifiable digital credentials program in Utah. We are private sector participants in NIST's National Cyber Security of Excellence initiative for privacy-preserving digital ID.

We are hiring skilled engineers who care about making a real impact in improving public services, digital autonomy, and user privacy for the world. We work closely with public sector agencies, and have high regard for public servants. We have a strong engineering and customer-oriented culture, and are not simply a SaaS product or AI wrapper. Our roles are not for the faint of heart: you will be expected to work hard and learn a lot in this role.

Our engineers are ambitious to get outcomes for our customers and their constituents. On any given day, they may write great Rust/C#/TypeScript, deal with mainframe dumps, read policy documents, respond to technical RFIs/RFPs, manage on-prem environments, implement new NFC + Bluetooth protocols in Swift/Kotlin, create CI/CD processes that enforce W3C accessibility guidelines and i18n requirements, rewrite lost specs from disassembled binaries, figure out stablecoin payments, and design new protections for public key infrastructure. It is a team effort, and people with T-shirt shaped skills are able to collaborate and learn a ton from each other every day.

We are interested in candidates who want to be proud of the meaningful impact they make for society, even if it takes time to get right. This is not the right job for someone who wants to "join a cool new AI startup" that implodes or exits in under a year.

See our roles here: https://jobs.lever.co/sprucesystems/

Osaurus | Full-Time | Remote | Protocol Engineer

Osaurus is a native macOS AI platform. The core idea: inference is a commodity — everything else (context, memory, tools) should be owned by you, locally. Think of it as the runtime layer for AI on Mac that works with any provider (OpenAI, Anthropic, xAI, local models via MLX).

3.7K+ GitHub stars and 54K+ downloads with zero marketing spend. Open source, local-first, provider-agnostic.

Looking for a protocol engineer who wants to build agent-to-agent networking and communication infrastructure. You'd be the first hire.

What we work with: Swift, macOS native APIs, Apple Silicon optimization, provider-agnostic API layer, plugin architecture. You don't need Swift experience specifically — strong systems fundamentals and the ability to pick things up fast matter more.

If this sounds interesting, try the app (https://github.com/osaurus-ai/osaurus), share your GitHub, and tell me what you'd change.

t@osaurus.ai