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Some Software Design Principles

Some Software Design Principles 1. Don’t Repeat Yourself (DRY) 2. Keep It Simple, Stupid (KISS) Making something complex is easy, but making something complex simple is difficult. 3. Program to an interface, not an implementation Prefer composition over inheritance Dependency inversion principle 4. Command-Query Separation (CQS) Query: when a method returns a value to answer a question Command: when a method changes the state of an object 5. You Ain’t Gonna Need It (YAGNI) Only design and implement what is necessary. Avoid overengineering. Implement what you need now; add more when needed later.

Tuesday, April 18, 2023 Read
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On High Availability Systems

On High Availability Systems Item / Mechanism Backups M/S MM 2PC Paxos Consistency Weak Eventual Eventual Strong Strong Transactions No Full Local Full Full Latency Low Low Low High High Throughput High High High Low Medium Data loss Lots Some Some None None Failover Down Read only Read only Read/write Read/write This table essentially covers the foundational solutions for high-availability systems today. M/S and MM are not hard to implement, but have many issues. 2PC suffers from poor performance, while Paxos is too complex and difficult to implement.

Tuesday, April 18, 2023 Read