Redundancy means duplicating critical data or services to increase the system's reliability. — For example, if only one copy of a file is stored on a single server, then losing that server means losing the file. Since losing data is seldom a good thing, we can create duplicate or redundant copies of the file to solve this problem. This same principle applies to…

A proxy server is an intermediary piece of hardware/software that sits between the client and the back-end server. — It receives requests from clients and relays them to the origin servers. Typically, proxies filter requests, log requests or sometimes transform requests (by adding/removing headers, encrypting/decrypting, or compression). Another advantage of a proxy server is that its cache can serve many requests. …

Indexes are used to improve the speed of data retrieval operations on the data store. — An index makes the trade-offs of increased storage overhead and slower writes (since we have to write the data and update the index) for the benefit of faster reads. Indexes are used to quickly locate data without examining every row in a database table. …

Data partitioning (also known as sharding) is a technique to break up a big database (DB) into many smaller parts. — It is the process of splitting up a DB/table across multiple machines to improve an application's manageability, performance, availability and load balancing. …

CAP theorem states that it is impossible for a distributed software system to simultaneously provide more than two out of three of the following guarantees (CAP): Consistency, Availability and Partition tolerance. — When we design a distributed system, trading off among CAP is almost the first thing we want to consider. CAP theorem says while designing a distributed system, we can pick only two: Consistency

By definition, Design Patterns are reusable solutions to commonly occurring problems(in the context of software design). — Design patterns were started as best practices repeatedly applied to similar problems encountered in different contexts. They became popular after they were collected, in a formalized form, in the Gang Of Four book in 1994. Originally published with C++ and Smalltalk code samples, design patterns are very popular in Java…

A Primer on Public Key Cryptography, Encryption, Blockchains, and Mining. — Public Key Cryptography This notion of public-key encryption is one of the greatest inventions in human history. If you think about ciphers from the pre-World War I era and war, you would have the same key to encrypt and decrypt. …

A few fundamental algorithms are considered important for developers and all tech roles. — Software developers care much more about your ability to create a new algorithm than memorizing an existing one. Still, these come up frequently enough that it’s worth your time to remember them. Sorting The two most common good ways to sort an array are Quick Sort and Merge Sort. The others…

Depending on what you’re optimizing for, there are many different approaches to holding or organizing your data. — As its name suggests, a data structure is a structure for holding data. In roughly descending order of importance for an interview, the common data structures are: Array An array is the most straightforward way to hold a set of objects. It stores items in a simple list of objects. Looking…