Staff/Senior Software Engineer, Hybrid IR and Systems
Confirmed on the employer's own hiring board on Oct 10, 2026. First seen by Alion on Aug 24, 2026.
Staff/Senior Software Engineer, Hybrid IR and Systems
New York City | Full-time | On-site in SoHo, five days per week
Reports to the CTO and works directly with the founding team
ABOUT HELIOS
Helios is building a new kind of company to solve America’s hardest problems, starting with the government interaction layer.
Government shapes every consequential market, but the infrastructure connecting public institutions and private organizations remains fragmented, manual, and difficult to navigate. Helios is rebuilding that layer.
Our core platform, Proxi, gives organizations the intelligence they need to understand what government is doing, why it matters, and what to do next. From that foundation, we design and deploy secure, mission-specific systems for government agencies, enterprises, and institutions operating in complex and highly regulated environments.
We bring together frontier AI, deep public-sector expertise, and forward-deployed execution. Our team includes leaders and builders from the White House, U.S. Department of State, Datadog, and Microsoft. We are backed by leading institutional investors and trusted by organizations working on high-stakes problems across government and industry.
MISSION
As a search and information retrieval engineer at Helios, you will own the key components of the Helios Rapid Ontology System (H.R.O.S.), our long horizon temporal memory management and search system. This system is what powers Proxi’s lossless memory system, enabling traceable and auditable AI outputs for sensitive information environments. This also is used to power retrieval over our several hundred terabyte data corpora. Expected areas of expertise:
Retrieval mechanisms and their complementarity.
Analyzers, tokenization, field boosts and BM25 parameterization for lexical indices. HNSW parameters, quantization, shard design and recall against latency for vector indices.
Rank fusion, score normalization, learning to rank, cross encoder reranking, duplicate suppression and source coverage limits.
Query intent classification, entity linking, alias and acronym graphs, controlled expansion and translation of natural language into structured filters and facets.
Temporal modeling, valid vs. transaction time, supersession, corrections and effective date intervals.
Permission aware retrieval, including tenant isolation, PII filtering and cache key authorizations.
Relevance evaluation under sparse labels.
Multilingual and cross lingual retrieval.
KEY RESPONSIBILITIES
Own Proxi’s retrieval stack end to end, from corpus onboarding and index design through hybrid retrieval, fusion, reranking, reindexing, and backfills.
Advance our query-understanding and temporal-retrieval capabilities, including intent detection, entity resolution, structured filtering, and jurisdiction-, date-, and version-aware search.
Improve retrieval performance, reliability, and cost through capacity planning, caching, reranker optimization, and safe degradation under load.
Expand federated search across Proxi’s separate data collections, including source-aware query planning, filtering, score calibration, and result merging.
Enhance time as a first-class retrieval concept so users can search the correct version, status, or historical state of a record.
Improve the dynamic connection system to map documents and records to the people, organizations, agencies, events, and relationships they concern.
Expand support for multimodal content searchable through the same retrieval interface as Proxi’s continuously ingested datasets.
Own relevance quality and production performance, including evaluation, indexing, observability, authorization, provenance, and recovery.
NICE TO HAVE
Domain adaptation of embedding models through fine tuning, hard negative mining or distillation.
Work on policy, legislative, procurement, legal or healthcare corpora, where traceable information systems are mandatory.
Experience with transliteration and identifying entity names that should never be translated.
Operating search in classified, air gapped or forward deployed environments.
Open source contributions to search and ranking projects.
WORKING AT HELIOS
This is a full-time, in-person role based in our SoHo office in New York City. Team members are expected to work from the office five days per week when they are not deployed with customers.
Certain customer engagements may require background checks, security reviews, access approvals, or eligibility for a U.S. government security clearance. Some projects may be subject to U.S. citizenship or other customer-specific access requirements.
We're not looking for passengers; we want driven innovators with a hunger to build from the ground up - obsessed with pushing the boundaries of natural language understanding, document processing, and personalized relevance.
Helios is a fast-moving startup with ambitious goals. This is not a conventional 9-to-5 role. We expect flexibility during critical deployment periods, customer incidents, product launches, and other company-critical work. In return, this role offers unusual ownership, direct access to consequential institutions, and the opportunity to build systems that affect how major decisions are made.
HOW WE WORK
Own outcomes, not just assigned tasks. Identify what needs to happen and drive it through completion.
Move quickly without lowering the standard. Speed and rigor are complementary.
Stay close to the mission and the user. The best decisions begin with the real problem.
Work across boundaries. Everyone contributes beyond the narrow limits of a job title.
Communicate directly. We value clear thinking, honest feedback, and low-ego collaboration.
Build for the real world. Our systems must perform in complex, regulated, and high-stakes environments.
EQUAL OPPORTUNITY
Helios is an equal opportunity employer. We evaluate candidates based on their abilities, experience, and potential to contribute to our mission. We do not discriminate on the basis of race, color, religion, sex, gender identity or expression, sexual orientation, national origin, age, disability, veteran status, or any other status protected by applicable law.