System Design · Senior
High-Level Design / Architecture Pack
System-level architecture: tradeoff-driven design of services, data and infrastructure.
The HLD bar: architecture tradeoffs, data flows, failure modes, and the follow-ups that separate senior from staff.
- Questions
- 360
- Topics
- 20
- Pages
- 285pages
- 360 questions, every one with a model answer
- Architecture tradeoff framework
- Data & infra decisions
- Failure-mode analysis
- Follow-up question drills
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What is inside
20 chapters, in the order the interviews tend to ask them:
- Framing requirements, constraints and scope
- Estimation and sizing the workload
- Capacity, headroom and resource planning
- Latency budgets and tail behaviour
- Stateless services and horizontal scale-out
- Load balancing and traffic management
- Partitioning and sharding strategies
- Replication, leader election and failover
- Consistency models and replication trade-offs
- Transactions, idempotency and exactly once effects
- Relational modelling and index strategy
- Storage engines and the data lifecycle
- Caching layers, staleness and invalidation
- Messaging, queues and stream processing
- Rate limiting, backpressure and load shedding
- Reliability objectives, error budgets and retry policy
- Observability, objectives and operational signals
- Deployment, migration and schema change safety
- Failure mode analysis and resilience review
- Presenting and defending the architecture decision
How the answers are built
Each chapter opens with the checklist the question is really testing. A few from this pack:
- A constraint you can test is a number or an observable behaviour, never an adjective.
- A sizing model is a set of named assumptions you expect to be revised.
- The first saturated layer defines capacity, so instrument every layer before you scale any.
- A budget is an allocation across named stages, and each stage has an owner.
- In process state is a scaling constraint even when it looks small and per user.
- The balancer is a policy engine, so the algorithm is a design decision to document.
Questions this pack covers
- A stakeholder asks for a system that stays up during a sale. How do you turn that into something testable?
- What belongs in the context section of an architecture decision record?
- How should a sizing estimate be recorded so that it can be falsified later?
- Which unit of work should a throughput model be derived from?
- How do you identify which resource will bind first before launch?
- What scenario should a headroom number be justified against?
- How do you split a latency budget across services when you do not own all of them?
- Which dependencies are on the critical path, and how do you prove it?
Each one is answered in full in the pack, with the reasoning written out rather than a bullet list.
About this pack
- How many questions?
- 360, spread across 20 topics, written out in full across 285 pages.
- Do the answers just list keywords?
- No. Each answer is written as prose, because that is what you have to reproduce when someone asks you the question.
- How do I get it?
- Pay once and the PDF arrives by email immediately, with a signed download link.
- Can I get it refunded?
- Yes, if it is not what you expected. See the refund policy.
