About Challenge
Vassar Labs is hiring Java engineers across three tracks — 0–3 years (Software Engineer), 3+ years (Senior Software Engineer) and 6+ years (Tech Lead) — to build the climate-technology platforms that Indian state governments run on: flood early warning, reservoir operations, urban water supply and digital agriculture.
This is a hireathon, not a contest. There is no prize pool and no leaderboard. There is one 1-hour online test, a one-day onsite hackathon at our Hyderabad office, and — for everyone who clears the hackathon — an interview opportunity: two technical rounds, and nothing else. Your build and your code walkthrough do the work the rest of a normal interview loop would have done.
We are looking for engineers who can build a system and keep it running — people who write real Java, model data in SQL and NoSQL, move it through streaming pipelines, and have stood up the open-source infrastructure underneath it themselves.
Eligibility Criteria
- Experience: Track 1 — 0–3 years (Software Engineer) · Track 2 — 3+ years (Senior Software Engineer) · Track 3 — 6+ years (Tech Lead). 2024–2026 graduates with strong Java projects may apply to Track 1.
- Location: Roles are based in Hyderabad. The online test is remote; the finale must be attended in person.
- Backgrounds: Backend engineering · Platform / infrastructure engineering · Data & streaming engineering · Systems and distributed design.
- Must have: Working SQL and at least one NoSQL store, plus one stream-processing framework — whichever one you have used; we do not care which.
- Must have: Hands-on experience self-hosting open-source infrastructure — you have installed, configured, tuned and debugged it yourself, not only consumed a managed cloud service.
- Language: The programming question is Java only (8 / 11 / 17 / 21). The SQL question is standard ANSI SQL, graded on a standard relational engine.
- Current Vassar Labs employees and their immediate teams are not eligible.
Challenge Format
Two rounds to get in front of us, then two technical interviews — a process designed to find engineers who build and operate production systems, not to rank them.
Online test · 1 hour
MCQs, 1 programming question and 1 SQL question. Proctored, Java only, same window for everyone.
Shortlisting
Scored per track against its own paper. Shortlisted candidates get the onsite logistics and the tech brief.
1-day onsite hackathon
Hyderabad office. Problem drop at 9 AM, six hours of build, demo and code walkthrough to a panel.
2 technical rounds
Clearing the hackathon earns the interview — two technical rounds only, then the offer.
Clearing the hackathon is what gets you the interview — and the interview is two technical rounds, not the usual four-round loop.
Tracks
Three tracks, one per experience band. Pick yours at registration, based on your total professional experience — if you have 6+ years, take the Tech Lead track. Each track has its own paper, its own onsite problem and its own panel, so you are never compared against someone at a different stage of their career.
Software Engineer
- Build a REST service against a real spec, onsite
- A Java web framework, a datastore, tests, a clean demo
- We look for solid fundamentals and readable code
Senior Software Engineer
- Extend a live service under changing requirements
- API design, streaming flow, behaviour under load
- We look for engineers who have operated what they built
Tech Lead
- Architect a high-throughput ingestion platform
- Build the critical slice, lead a pair, defend the design
- We look for depth, hands on infra, and judgement
Skills we are hiring for
01 · Core Java & services
- Collections, generics, records
- Concurrency & the memory model
- Java web framework, REST, ORM
- Testing that actually runs
02 · SQL & NoSQL
- Joins, windows, CTEs, EXPLAIN
- Indexes and why it got slow
- Document & wide-column stores
- Partition keys & consistency
03 · Streaming & pipelines
- Message log: partitions, groups, lag
- Any stream-processing framework
- Windows, watermarks, late events
- Exactly-once, checkpoints, replay
04 · Self-hosted infrastructure
- Install, configure, tune, upgrade
- Linux, JVM flags, disks, GC
- Containers & orchestration
- Metrics, dashboards, logs
The stack you would join
Java 17/21 · a Java web framework and ORM · a relational database with geospatial extensions · document and wide-column stores · an in-memory cache · a search engine · a distributed message log · a stream-processing framework · distributed batch processing · workflow orchestration · containers and orchestration · Linux · metrics and dashboards · Python AI-ML services — most of it self-hosted on our own clusters.
What We're Looking For
Across all three tracks, the panel is trying to answer four questions:
- Can you write Java that others can maintain? Idiomatic, tested, and boring in the right places.
- Can you model data properly? Knowing when a relational schema is right, when a wide-column store is right, and what you give up either way.
- Have you run it in anger? A lagging consumer, a stuck streaming job, a full disk, a GC pause at the worst moment — we want people who have been there.
- Do you know when to stop? The judgement to say no to complexity matters more the more senior the track.
What we are not testing: competitive-programming tricks, puzzle questions, or framework trivia you would look up in ten seconds.
Timeline
- 18 SEP – 09 OCT 2026Registration window
Sign up and pick your role. Registrations close at 11:59 PM IST on 9 October.
- SAT, 10 OCT 2026 · 10:00–11:00 AM ISTRound 1 — online test
60 minutes, proctored. MCQs, one programming question in Java, one SQL question.
- 16 OCT 2026Shortlist announced
Results by email and on your dashboard. Shortlisted candidates receive the onsite logistics and the tech brief.
- SAT, 24 OCT 2026 · 9:00 AM – 7:00 PMRound 2 — onsite hackathon
At our Hyderabad office. Problem drop, six hours of build, demos to the panel, interviews woven through the day.
- 26–29 OCT 2026Two technical rounds
Candidates who clear the hackathon are invited to interview — two technical rounds, scheduled at your convenience, online or at the office.
- BY 30 OCT 2026Results & offers
Decisions communicated and offer letters issued.
What you get
- A role, not a ranking. A full-time Java role on our platform teams in Hyderabad. No prize money — this is a hireathon.
- A short loop. Clear the hackathon and you go straight to two technical rounds — no repeat screening, no month of scheduling.
Register for your track
Registration is per track — pick the one that matches your experience and you will be sent the paper set for it.
One registration per candidate. If you are on a boundary, pick either adjacent track and mention it in the form.
FAQs
Is there prize money?
No — and that is deliberate. This is a hireathon: the outcome is a job offer, not a cash prize or a leaderboard rank. Participation is free.
Is the test the same for all three roles?
Same shape, different difficulty. Every candidate gets 60 minutes, a set of MCQs, one programming question and one SQL question. Track 1 sits at easy–medium, Track 2 at medium–hard and Track 3 at hard — with the senior tracks pulling more from NoSQL, streaming and infrastructure.
Which track should I pick?
Go by total professional experience: 0–3 years is Track 1, 3+ years is Track 2, and 6+ years is Track 3. If you have 6+ years, take Track 3 — that is the paper and panel calibrated for you. On a boundary (3 years exactly), pick either adjacent track and mention it at registration; we will not penalise the choice.
Which language can I code in?
Java only for the programming question — Java 8, 11, 17 or 21. The SQL question is standard ANSI SQL, graded against a standard relational engine. In Round 2 the service you build must be Java on the JVM; frameworks and supporting scripts are your choice.
What do you mean by “hands-on with self-hosted open source”?
We run our own clusters — messaging, stream processing, relational and NoSQL stores, and the monitoring around them — rather than renting managed equivalents. So we look for people who have done the same at some scale: installed it, configured it, tuned the JVM and the disks, watched it fall over, and fixed it. A managed-service-only background is not a disqualification for the Software Engineer role, but you should have run something yourself, even if only on a home lab.
Which stream-processing framework do I need to know?
Any one of them, known properly. We care that you understand windowing, watermarks, late and out-of-order events, checkpointing and backpressure — the framework you learned it in matters much less than whether you have debugged a job that was falling behind.
What happens after the hackathon?
Clearing the hackathon gets you an interview opportunity: two technical rounds, and nothing beyond that. The build and the code walkthrough from the onsite day carry into those conversations, so the rounds go deep rather than starting over.
What happens if I cannot attend the onsite round?
The finale is in person by design — it is where the hiring decision is made. If a genuine emergency stops you attending, write to us before the day and we will move you into the next hiring cycle rather than disqualify you.
Is there any fee to participate?
No. Registration, both rounds and the onsite day are free.
Instructions
Read these before the test window opens on 10 October 2026.
Before the test
- Use a stable internet connection. Tethering via a mobile device is not advised.
- Take the test on a laptop or desktop with a working webcam. Mobile devices are not supported.
- Check your camera, microphone permissions and browser compatibility at least a day in advance.
- Attempt the test in an incognito or private window so that browser extensions do not interfere.
- Sit alone in a quiet, well-lit room with your face clearly in frame.
During the test
- Once the test starts, the timer cannot be paused. You have to complete it in one attempt.
- Do not close the browser window or tab before you submit your final answers.
- The test is webcam and screen proctored, with tab-switch detection. No second device, no second person in the room.
- AI assistants, shared solutions and outside help are not allowed in Round 1.
- You may submit a question multiple times; the best submission is considered. Partial scoring applies to all three sections.
- If your connection drops, your submitted answers are saved — log back in and continue. The timer keeps running.
Sections
- MCQs — 20 questions. Select the correct option; there is no negative marking.
- Programming — 1 question, Java only (8 / 11 / 17 / 21). Write and run your code in the editor, then submit. Watch the time and memory limits.
- SQL — 1 question against a provided schema, standard ANSI SQL, graded on a standard relational engine.
Round 2 — onsite, and what follows
- The test is 60 minutes end to end; plan your time across the three sections before you start.
- Bring a government photo ID and your own laptop with a working Java toolchain.
- Clearing the hackathon earns you an interview opportunity — two technical rounds, and that is the full loop.
- You may use AI assistants during the onsite build, and you must be able to explain every line you submit.
- Your onsite code stays yours. We review it only for hiring and never ship it.
Conduct
- One registration per candidate. Duplicate accounts are disqualified.
- Any form of plagiarism or impersonation ends your participation immediately.
- Vassar Labs' decision on shortlisting, evaluation and offers is final.
Questions about the process? Write to careers@vassarlabs.com.
Company
Vassar Labs
Vassar Labs builds climate-technology platforms — AI/ML, IoT, remote sensing and digital twins — that state governments run on. Our systems forecast floods before they arrive, tell a farmer what their field needs this week, schedule releases from reservoirs, and help cities find the water they are losing.
It is Java at the core: high-volume ingestion through message streaming and stream processing, geospatial and time-series data across SQL and NoSQL stores, and services that cannot be down when a river is rising. We host that stack ourselves — which is why we hire people who can run it.
Headquarters: 5th Floor, Tower 9, Mindspace IT Park, Madhapur, Hyderabad 500 081. vassarlabs.com