Manage Context Windows in an Applied AI System
Company: Rogo
Role: Machine Learning Engineer
Category: ML System Design
Difficulty: medium
Interview Round: Onsite
# Manage Context Windows in an Applied AI System
Design the context-building layer for an applied AI assistant. It must combine the current request, conversation history, retrieved evidence, and tool results while staying within a model's context limit and keeping important evidence traceable.
### Constraints & Assumptions
- The model has a fixed token budget shared by input and expected output.
- Retrieved documents can conflict, repeat one another, or contain untrusted instructions.
- Conversation history can grow indefinitely.
- The system must explain which evidence supported the answer.
### Clarifying Questions to Ask
- Which information is authoritative, and which is merely conversational context?
- What output-token reserve and latency target are required?
- Can old conversation turns be summarized, and must summaries be reversible to source turns?
### Part 1 — Context construction
Propose a budget and ordering policy for system instructions, user request, history, retrieved evidence, and tool results.
#### What This Part Should Cover
- A token budget with output reserve
- Priority and truncation rules
- Deduplication and provenance
### Part 2 — Safety and quality
Handle prompt injection, conflicting evidence, stale summaries, and evaluation of context selection.
#### What This Part Should Cover
- Trust boundaries and instruction hierarchy
- Evidence recency and conflict reporting
- Retrieval and answer-quality measurements
### What a Strong Answer Covers
- A deterministic context policy
- Traceable evidence and summaries
- Evaluation that separates retrieval from generation
```hint Budget by information role
Do not concatenate until the limit is reached. Reserve explicit budgets for instructions, user intent, evidence, history, and output, then choose content within each role.
```
### Follow-up Questions
- When should a larger-context model be chosen?
- How would you detect that summarization removed a critical constraint?
Quick Answer: An applied-AI system-design interview about building model context from user requests, conversation history, retrieved evidence, and tool results. It tests token budgeting, evidence ranking, summarization, provenance, prompt-injection boundaries, and graceful degradation.