Day 74: Mock Interview 3: Frontend/Mobile System Design
Run a full timed system design mock on an unfamiliar prompt, applying the Day 66 framework and Day 67-69 trade-off instincts together.
Study
Concepts
This mock is about synthesis, not new material
By this point you have the framework (Day 66), the trade-off analyses (Days 67-69), and 5 worked examples (Week 10) — this mock tests whether you can synthesize all of it live, on a prompt you have not seen structured for you in advance, which is a meaningfully different skill from following an already-outlined case study.
Choose a prompt outside anything already covered explicitly: "Design the frontend architecture for a food delivery app's live order-tracking screen" is a good choice — it touches real-time data (Day 43, 46), maps/location UI, offline degradation (Day 45), and has natural depth for a 15-20 minute deep dive, without being a copy of a Week 10 case.
See It
Visualizations
Visualization
This mock, mapped to prior days
from Day 66
from Days 29, 43, 67
from Days 45, 46
from Day 66 phase 4
Build It
Code Examples
Run this exactly like Day 70, on a new prompt
Prompt: "Design the frontend architecture for a food delivery app's
live order-tracking screen — the user watches their driver's location
update in real time on a map, with status updates (preparing, picked
up, arriving) and an ETA."
Give yourself 45 minutes, no notes, and hit every phase from Day 66:
1. Clarify requirements (functional + non-functional) — don't skip this.
2. High-level architecture — what pushes location updates, how the
client renders them, what happens offline/on a dropped connection.
3. Deep dive — the interviewer (or you, playing that role) picks ONE:
the real-time transport choice, or the offline/reconnection story,
or map-rendering performance with frequent position updates.
4. Trade-offs — name at least one alternative you rejected and why.
5. Wrap-up — what would you monitor once this ships?
Self-review immediately after using the Day 70 scorecard.Remember
Key Takeaways
- This mock tests synthesis across the whole system-design track, not recall of any single day.
- Deliberately choose a prompt with no pre-built structure to answer against — that is the actual interview condition.
- Real-time UI prompts naturally pull in networking (Day 43), offline-first (Day 45), and rendering trade-offs (Day 29/67) together — notice how the days connect.
- Reuse the Day 70 self-review scorecard every time — consistency in review is what compounds improvement across mocks.
- If a deep-dive area feels shaky, that is exactly the signal for what to re-study before the NEXT mock — use these mocks diagnostically, not just as rehearsal.
Do It
Practice
- 1Run the food-delivery tracking prompt above as a full 45-minute timed mock, narrating out loud.
- 2Self-review with the Day 70 scorecard and identify your weakest phase for this specific mock.
- 3Write one NEW system design prompt of your own (not listed anywhere in this roadmap) for a future mock.