jian 2nd period

chap02/[chap02]정지안.md

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+# Back-of-the-envelope Estimation
+
+The act of conducting experiments to estimate values based on universally accepted performance metrics
+
+To assess whether a design meets the requirements
+
+## Latency Value
+
+| Operation | Latency(ns) |
+| --- | --- |
+| L1 Cache reference | 0.5 |
+| Branch Mispredict | 5 |
+| L2 Cache reference | 7 |
+| Mutex lock/unlock | 100 |
+| Main memory reference | 100 |
+| 1kB compression using Zippy | 10,000 |
+| Transmitting 2KB over a 1Gbps network | 20,000 |
+| Contiguosly read 1MB from memory | 250,000 |
+| Round-trip message latency within the same data center | 500,000 |
+| Disk seek time | 10,000,000 |
+| Contiguosly read 1MB from network | 10,000,000 |
+| Contiguosly read 1MB from disk | 30,000,000 |
+| Round-trip packet latency from California to the Netherlands | 150,000,000 |
+
+Conclusions
+
+- Memory is fast, but disk is still slow
+- Avoid disk seeking as possible
+- Simple compress algorithm is fast
+- Compress data before transmitting them via internet
+- Transmitting data between data centers shows high latency
+
+## Metrics related to High Availability
+
+High Availability: The ability of a system to operate continuously without interruption for extended periods of time
+
+100% → Never having experienced any downtime
+
+Typically, services aim for availability values of 99% or higher
+
+Service Level Agreement(SLA): An agreement between the service provider and the customer
+
+The uptime of the service provided by the service provider is officially documented
+
+## Tips
+
+- Do rounding and approximation rather than performing complex calculations with precision
+- Write down assumptions for later reference
+- Always specify units to prevent ambiguity
+- Typically, problems involving QPS (Queries Per Second), maximum QPS, storage requirements, cache requirements, and server count estimations arise frequently
+
+# Strategies for System Design Interviews
+
+System Design Interviews ⇒ 
+
+Demonstrating design skills and the ability to defend decisions made during the process
+
+1. Understanding the problem and defining the scope of the design
+
+    It is risky to provide answers without fully understanding the requirements
+
+    → red flag
+
+    Gather necessary information for system construction through questioning or making assumptions (**Write down assumptions for later reference)**
+
+2. Presenting a rough design proposal and seeking agreement
+
+    Present the initial blueprint of the design to the interviewer and seek feedback
+
+    Calculate rigorously whether the initial design meets the constraints related to the system's scale
+
+3. Detailed design
+
+    Identify the key areas of focus and prioritize the components based on their importance and interdependencies
+
+4. Conclusion
+
+    Never say that there’s no room for improvement
+
+    It's also beneficial to summarize the design and explain potential issues that may arise if errors occur
+
+
+Dos
+
+- Confirm through questioning
+- Understand the requirements
+- Keep in mind that there is no single correct answer
+- Communicate with the interviewer
+- Start from the most important component
+- Never give up
+
+Don’ts
+
+- Don't prepare for typical interview questions
+- Present the design before understanding the requirements
+- Get caught up in details from the start

chap03/[chap03]정지안.md

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+# Strategies for System Design Interviews
+
+System Design Interviews ⇒ 
+
+Demonstrating design skills and the ability to defend decisions made during the process
+
+1. Understanding the problem and defining the scope of the design
+
+    It is risky to provide answers without fully understanding the requirements
+
+    → red flag
+
+    Gather necessary information for system construction through questioning or making assumptions (**Write down assumptions for later reference)**
+
+2. Presenting a rough design proposal and seeking agreement
+
+    Present the initial blueprint of the design to the interviewer and seek feedback
+
+    Calculate rigorously whether the initial design meets the constraints related to the system's scale
+
+3. Detailed design
+
+    Identify the key areas of focus and prioritize the components based on their importance and interdependencies
+
+4. Conclusion
+
+    Never say that there’s no room for improvement
+
+    It's also beneficial to summarize the design and explain potential issues that may arise if errors occur
+
+
+Dos
+
+- Confirm through questioning
+- Understand the requirements
+- Keep in mind that there is no single correct answer
+- Communicate with the interviewer
+- Start from the most important component
+- Never give up
+
+Don’ts
+
+- Don't prepare for typical interview questions
+- Present the design before understanding the requirements
+- Get caught up in details from the start