Synthflow AI is a no-code platform for deploying voice AI agents that automate phone calls across contact center operations and business process outsourcing (BPO) at scale. We help mid-market and enterprise companies manage routine calls to save teams time and resources.

Our agents have already delivered measurable impact:

Over 5 million hours of contact center operations saved
35% more calls answered compared to non-AI operators
45 million calls handled with a 99.9% uptime

Backed by Accel, Atlantic Labs, and Singular and trusted by over 1,000 customers, our growth leads an industry shift toward sophisticated and accessible conversational AI.

The Role

We’re hiring an Applied LLM Engineer who lives and breathes prompt engineering and writes excellent production-grade Python. You’ll run a tight feedback loop with customers, turn real conversations into better prompts and eval datasets, and ship changes that measurably improve agent outcomes. This is a highly applied role working directly with customer feedback.

What You’ll Do

Design & iterate prompts (system, tool/function-calling, task prompts) to boost voice AI agent success, reliability, and tone.
Build co-pilots for customers to author their own prompts: meta-prompted assistants that suggest structures, lint for risks, autocomplete tool schemas, critique drafts, and generate eval cases.
Work directly with customer feedback and conversation logs to identify failure modes; translate them into prompt changes, guardrails, and data improvements.
Build eval datasets (success labels, rubrics, edge cases, regressions) and run offline/online evaluations (A/B tests, canaries) to quantify impact.
Create Python utilities/services for prompt versioning, config-as-code, rollout/rollback, and guardrails (policies, refusals, redaction).
Partner with PM/Success to define success metrics (task completion, first-pass accuracy, cost, latency) and instrument dashboards/alerts.
Own LLM integration details: function/tool schemas, output parsing/validation (pydantic), retrieval-aware prompting, and fallback strategies.
Ensure privacy & compliance (PII handling, anonymization, regional data boundaries) in datasets and logs.
Share learnings via concise docs, playbooks, and internal demos.

Must-Have Skills

Python: 3+ years writing clean, tested, production code (typing, pytest, profiling); experience building small services/APIs (FastAPI preferred).
Prompt Engineering: Hands-on experience designing system/tool prompts, meta-prompting, rubric graders, and iterative prompt tuning based on real user data.
LLM Integration: Comfortable with major APIs (OpenAI/Anthropic/Google/Mistral), function/tool calling, streaming, and robust output handling.
Evaluation Mindset: Ability to define measurable success, create labeled datasets, and run methodical experiments/A/B tests.
Product Sense: Comfortable talking with customers, turning qualitative feedback into shipped improvements.
Data Hygiene: Practical experience cleaning, labeling, and balancing datasets; awareness of privacy/PII constraints.

Nice-to-Haves

Experience building prompt-authoring UIs/SDKs or internal tooling for prompt versioning and governance.
Agentic frameworks & tooling: DSpy, MCP, LangGraph, LlamaIndex, Rasa; experience with agent/tool schemas and orchestration.
Observability & eval tooling: Langfuse, LangSmith, Braintrust; building eval harnesses and experiment dashboards.
RAG & vector stores: Qdrant/Weaviate/Pinecone and retrieval-aware prompting.
Experimentation workflows: A/B testing, prompt diffing/versioning.
Infra & analytics: light SQL/log analysis, metrics & tracing, simple Grafana/OTel dashboards.
Writing public blog posts or talks about applied LLM techniques.

Interview Process

30-min intro screen – background, role fit, questions both ways.
Practical exercise (Prompt + Python) – design a prompt strategy, a customer-facing co-pilot flow, and a small eval harness.
Team interviews – deep dive on product mindset, experimentation rigor, and collaboration.
Founder/Leadership chat – scope, impact, and ways of working.

Why Join

Own the reasoning layer and the customer co-pilot experience used at scale.
Ship fast in a tight customer feedback loop and see your impact measured in days, not quarters.

Founded in Berlin in 2023 by serial entrepreneurs Albert Astabatsyan, Hakob Astabatsyan, and Sassun Mirzakhan-Saky, Synthflow AI democratizes access to advanced voice AI with a no-code platform that lets enterprises easily create, deploy and scale natural-sounding, cost-effective voice agents tailored to their business needs.

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Applied LLM Engineer - Prompts, Evals & Agents