Upwave (YC S12) | Senior Software Engineer | REMOTE (US) | Full-time | $150k-$175k + bonus/equity/benefits | https://www.upwave.com/job/8547924002/

Upwave builds brand measurement software for large advertisers, agencies, and media partners. We process high-volume ad exposure + survey/event data and turn it into brand lift, reach validation, optimization recommendations, and AI-assisted analysis for enterprise marketers.

We're looking for a senior full-stack/backend-leaning engineer who likes owning real production systems end to end. The strongest candidates for us tend to have concrete experience with JVM/Spring/Kotlin or similar backend systems, SQL/data modeling, AWS/Kubernetes/observability, and high-volume event or analytics pipelines. AdTech/MarTech/measurement experience is a plus, but not required if you enjoy learning messy business domains deeply.

The work includes building APIs and data pipelines, productionizing analytics/statistical workflows with Product and Data Science, improving reliability/performance, and building AI-powered customer experiences around our internal AI analyst, Bayes. Stack includes Kotlin/Java, Python analytics services, React, MySQL, DynamoDB, AWS, Kubernetes, Terraform and LLM orchestration.

We're profitable/growth-stage, remote-first in the US, and engineering-led: high velocity through focus and leverage, not crunch. Interview process includes an in-person meeting.

Apply: https://www.upwave.com/job/8547924002/ Or email me directly: jason.kelly@upwave.com

Felt Clinic (https://feltclinic.com) | Web Engineer | Remote (US Only) | Full-time | $180k-$200k

Felt Clinic is building the first embedded care SDK for health apps. Our mission is to make access to a doctor simple and secure inside any mobile application. We want teams to stop worrying about provider contracting and focus on building awesome experiences. We're looking for a NextJS Engineer to help us scale our platform. You’ll be developing powerful SDKs and APIs, integrating real-time communication tools, and shaping next-generation digital health experiences.

Tech Stack:

- Mobile: SwiftUI (iOS), Kotlin (Android), Ionic

- Web: Next.js, Turborepo, TypeScript

- Communication: WebRTC

What sets exceptional candidates apart:

- Hands-on experience working on mobile platforms (Swift/Kotlin)

- Expert with Next.js and RSC

- Stoked about healthcare experiences

- Deep expertise in full-stack product development

Felt has three name-brand Apps actively using our SDKs and anticipating approximately $10m ARR by late 2026. We’re backed by leading investors including 1984, Scrum Ventures, and Tau Ventures. Join us as we scale to build next-gen HealthKit on steroids.

Attendi | Senior Mobile Engineer | Amsterdam, Netherlands | ONSITE (hybrid) | Full-time (80–100%, ~4–5 days/week) | Visa sponsorship + 30% ruling possible

Company: Healthcare professionals spend too much time on admin when they should be delivering care. Attendi is building the Dutch healthcare sector's voice-enabled (digital) notepad: an intuitive tool for capturing and structuring medical data at the point of care. We have product-market fit and are scaling from ~100 healthcare organisations to 10x our userbase over the coming year. Our first native Android and iOS apps are already released and in daily use (https://apps.apple.com/nl/app/attendi/id6757230193), and we're looking for someone to lead their development.

Role: As our senior mobile engineer you'll own these apps end to end: building and maintaining the native Android and iOS clients, plus our open-source microphone SDKs (https://github.com/attenditechnology/attendi-android and https://github.com/attenditechnology/attendi-ios).

Stack: Kotlin (Jetpack Compose) on Android, Swift (SwiftUI) on iOS.

Apply: https://attendi.recruitee.com/o/senior-native-androidios-mob... - or email omar [at] attendi [dot] nl with something you've shipped. Mention HN.

Fold | Remote (US Only) | Senior Back End Engineer | Full-time

Fold is a publicly listed bitcoin financial services company building the tools people need to earn, buy, sell and live on Bitcoin. We're looking for a Senior BE Engineer to help build the financial infrastructure behind our products - payment processing, ledger systems, card transaction flows and event-driven pipelines.

  - 5+ years software engineering experience
  - Strong in: Java or similar (Kotlin, Scala, C#)
  - Experience with: production microservices, distributed systems
  - Familiar with: messaging/event streaming (Kafka, Pulsar)
  - Solid relational database and data modeling skills
  - Nice-to-have: fintech, payments, ledger/accounting domains
  - Nice-to-have: event-driven architectures, CQRS, event sourcing
  - Nice-to-have: Micronaut, Quarkus or similar modern Java frameworks
  - US residency (regulatory requirement)

Benefits: - Competitive salary + equity - 401k with 3% match - Unlimited PTO + yearly vacation stipend - Full health/dental/vision - Paid parental leave - Regular team meetups - Bitcoin starter pack (hw wallet included)

Email tiffany.sawhney (a) foldapp.com if you have questions or apply here: https://ats.rippling.com/fold-inc/jobs/514ba20e-a93e-4960-ad... [0] https://foldapp.com

Senior Software Engineer| New York City | Fintech

Tapitab is a stealth-mode fintech startup building a proprietary self-learning customer intelligence platform for the US hospitality industry. We are patent-pending across multiple core innovations and are moving fast toward launch.

We are looking for a Senior Software Developer to join our technical team and take full ownership of building our POS software layer — including payment integration, tab origination and settlement flows, and Android application development on a handheld payment device.

What We Need:

• 5+ years of Android development experience (Java or Kotlin) • Hands-on payment processor API integration — Stripe, Shift4, Fiserv, Worldpay, Finix, or equivalent • Deep knowledge of EMV, NFC, and contactless payment standards • Proven experience building POS software for bars, restaurants - hospitality industry • Prior work with leading POS system providers is a strong plus • Bachelor’s degree in Computer Science, Engineering, or a related field, or equivalent

What We Offer:

• Ground-floor opportunity at a stealth-mode startup with genuinely novel, patent-pending technology • Full contract basis at a competitive rate — OR — salary + equity for the right candidate • Work directly with the founding team on a greenfield architecture — no legacy code • Location: ONSITE - New York City

This is not a general dev role. We need someone who has built payment flows before and understands the hospitality POS environment from the inside.

Interested? Send your resume and a brief note on your POS and payments experience to:

info@tapitab.com

Santa Clara, CA | ONSITE | Android Engineer (AI-native, junior-friendly) | Jefit | $115K-$125K + equity + benefits

Jefit is a profitable fitness-tech company — 15+ years in market, no funding pressure, no enterprise red tape. We're hiring an experienced Android engineer to drive the Android side of our Adaptive Plan — a mesocycle-driven progressive-overload engine — end-to-end alongside our CTO. You'll see your code in front of millions of users every day.

What we care about (more than years on a resume):

You've shipped real Android products to Play Store — solo side projects count

Kotlin + Jetpack Compose + Coroutines, or you're actively learning them

AI-coding-assistant fluency is non-negotiable — Claude Code, Cursor, Copilot integrated into your daily workflow, not a name-drop

Offline-first / Room / SQLite mindset (we run in real gym environments where the WiFi is bad)

Extreme ownership end-to-end — feature, ship, polish, debug, repeat

We bias toward fast learners who already use AI to ship faster, over senior engineers stuck on a 2018 stack.

In-office in Santa Clara, CA. US work authorization required (no sponsorship).

Apply: https://tally.so/r/lbvOBN

Treasure AI | Staff Engineers (Fullstack/Backend) | HYBRID (Tokyo & Vancouver) | Full Time | https://www.treasure.ai/

You may know us from our open-source roots (Fluentd/Embulk.) We’re an enterprise CDP and agentic experience platform that unifies fragmented customer data from multiple sources and allows for complex marketing workflows. Our engineering team is distributed across Canada, Japan, and the USA.

We need three Staff Engineers (two in Tokyo, one in Vancouver) to act as technical anchors. You’ll be a great fit if you’re a backend/distributed systems engineer who can architect a clean React frontend, or a pure distributed systems specialist happy to collaborate across the full stack.

The roles primarily deal with architecting systems to process and personalize massive marketing datasets in near real time, with a strong emphasis on being able to work cross functionally to deliver best-in-class agentic interactions deeply integrated with our systems.

Our core stack is Rails, Typescript/Lambda, React, and Kotlin.

How to apply:

* Staff Fullstack (Tokyo) https://jobs.treasure.ai/jobs/542524-staff-fullstack-enginee...

* Staff Fullstack (Vancouver) https://jobs.treasure.ai/jobs/615459-staff-fullstack-enginee...

* More roles on our careers page (we are massively hiring): https://jobs.treasure.ai/

Starbridge | Senior Engineers (Kotlin/Java/React/Typescript) | NYC or Remote | Full-time |

[starbridge.ai](https://www.google.com/url?q=http://starbridge.ai&sa=D&sourc...)

Starbridge is building an AI platform that turns large-scale public and enterprise data into reliable sales insights. We are early, moving fast, and building from zero to one, so this role will have huge ownership and product impact.

Product Engineer: (React/Typescript) who would work closely with product and design to build user-facing parts of the platform. You will craft performant, stable frontends that explain technical concepts to non-technical users and help us iterate fast based on customer feedback.

AI Engineer: Applied AI plus strong software engineering. You will build, evaluate, and deploy LLM-driven features like deep document analysis and interactive chat, working with models from OpenAI, Anthropic, and Gemini. Expect hands-on Python, ML system design, experimentation, and production reliability. Bonus for RAG depth and frameworks like LangChain, LlamaIndex, or Hugging Face.

Backend Engineer: (looking for Kotlin/Java/Scala experience). You'll work across the backend: building enterprise integrations, large-scale scraping and parsing pipelines, and systems that let users apply LLMs to millions of documents to generate insights at scale.

We're looking to build our in-person team in NYC but also open to remote!

Apply: [https://starbridge.ai/careers](https://www.google.com/url?q=https://starbridge.ai/careers&s...) and mention HackerNews or email [recruiting@starbridge.ai](mailto:recruiting@starbridge.ai) with your resume.