Quick Answer
System design interview seven steps in English: clarify requirements, define APIs, estimate scale, sketch the data model, draw a high-level design, deep-dive two components, then hunt bottlenecks — narrate each step out loud.
Diagrams and what to say while drawing
Draw as you speak: requirements → APIs → estimates → boxes → deep dive → bottlenecks. Western panels score the narration as much as the diagram.
Key vocabulary
| Term | Plain meaning | Say it in an interview |
|---|---|---|
| Clarify | Ask scope before designing | “Just to confirm — are we designing for mobile clients too?” |
| API | System interface contract | “I’ll define postTweet and getTimeline first.” |
| Back-of-the-envelope | Rough scale math | “I’ll estimate QPS and storage next.” |
| Bottleneck | What breaks first at scale | “The bottleneck is the timeline fan-out.” |
ESL English phrases and transitions
Open and clarify
- “I’ll follow seven steps and narrate each one.”
- “First I’ll clarify functional and non-functional requirements.”
- “Stop me if you want to deep-dive a different component.”
UK/US system design moves
- “The tradeoff is X versus Y.”
- “I’ll deep-dive this component next.”
- “A single point of failure here would be …”
Pair this chapter with Mockly’s related article: spoken system design interview framework in english.
Key English language pitfalls
| Pitfall | Sounds like | Say instead |
|---|---|---|
| Jumping to Kafka | Sounds tool-led | State the problem, then the tool. |
| Silent drawing | Panel can’t follow | Narrate every box. |
| Skipping estimates | Misses scale sense | Say QPS before sharding talk. |
| Summary | Clear tradeoffs are how Western panels hear senior engineers. | |
Common English mistakes
| Mistake | Why it hurts | Fix |
|---|---|---|
| No clarify questions | Wrong design | Ask two scope questions first. |
| One deep dive forever | Unbalanced | Time-box; cover bottlenecks. |
| No tradeoffs | Junior signal | Always say what you give up. |
What the interviewer is testing
For the system design interview framework, UK/US interviewers test structured thinking, scale intuition, and calm spoken English — not accent perfection.
They listen for clarify → estimate → design → tradeoffs → bottlenecks. If those moves are audible, you sound hireable.
How to open in English
First 20 seconds
- “I’ll follow seven steps and narrate each one.”
- “First I’ll clarify functional and non-functional requirements.”
- “Stop me if you want to deep-dive a different component.”
system design interview step by step
Use this sequence for system design interview step by step. Say the step name before you do it.
| Step | What to say |
|---|---|
| Clarify | Functional + non-functional; who uses it; what’s out of scope. |
| APIs | Name core endpoints so the contract is visible. |
| Estimate | QPS, storage, bandwidth — order of magnitude. |
| Data model | Key entities and relationships on the board. |
| High-level | Boxes and arrows; clients → services → storage. |
| Deep dive | Two components with options and tradeoffs. |
| Bottlenecks | SPOF, hot keys, monitoring, failure modes. |
Weak vs strong answers
Weak
I’d use microservices and Kubernetes.
Strong
I’ll clarify read/write ratio first, estimate QPS, then choose a simple monolith-friendly design and only split services where the bottleneck forces it.
How to say the key terms
| Term | Say it |
|---|---|
| QPS | “queries per second” |
| SPOF | “single point of failure” |
| SLA | “service level agreement” |
Follow-up questions you will get
Expect these
- “Which component should I deep-dive — storage or fan-out?”
- “Do you want failure modes next or a caching plan?”
Practice drill
Set a timer for twelve minutes. Design the system design interview framework out loud in English. Record yourself. Check: clarify, estimate, tradeoffs, bottlenecks.
Repeat tomorrow focusing only on the deep-dive section.
Answer frameworks you can reuse
Clarify → APIs → Estimates → Data model → High-level → Deep dive → Bottlenecks.
For every deep dive: options → tradeoffs → recommendation.
Frequently Asked Questions
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