Category: tech

Distributed Caching Pattern: Write Through

Write-through caching is a caching mechanism where data modifications are written to both the source database and the cache. In this approach, every write operation triggers a write to a RAM cache (such as redis) and the source database (such as postgres). This is commonly used to complement look-aside caching pattern so that when subsequent […]

Questions to ask before caching with a remote cache

Distributed caching with a system like memcached or redis comes at a cost! If you haven’t added a remote cache yet, here’s some costs to consider: Even if you already operate or use a remote cache, caching any bit of data still adds complexity to your application – and not the essential kind. It’s easy […]

Forward Proxy vs Reverse Proxy

Two main types of proxies are forward proxies and reverse proxies. Since they’re both proxies, it’s not immediately obvious from their names how they’re different! All proxies act as a middle man in a network topology between two parties: the client (or thing requesting a resource) and a server (the thing providing the resource). The […]

Distributed Caching Pattern: Cache Aside

A distributed cache is a remote caching system that an application uses via a network to reduce read latency. There are lots of ways an application can interact with this cache and there tends to be common access patterns or strategies – one of the most popular access pattern is called “Cache Aside” (sometimes also […]

Newtons Square Root Method in Racket

Isaac Newton came up with an elegant method for calculating square roots through a series of approximations that get refined over time. At the end of this post, I will show a racket implementation of the procedure. Overview The square of can be written as either or in the exponential form . Therefore, the square […]

SICP Exercise 1.5 – Testing Evaluation Order

Prompt Ben Bitdiddle has invented a test to determine whether the interpreter he is faced with is using applicative-order evaluation or normal-order evaluation. To refresh your memory, “applicative-order” means that procedure arguments get evaluated before being substituted into a procedure. “Normal-order” means that procedure arguments get evaluated later and only ifneeded. He defines the following […]

Web Application Session Management Primer

Most web applications need to handle user sessions at some point. A common use-case is to remember an authenticated user across requests. Since HTTP is a stateless protocol, the only way for servers to know that the current request is related to a previous request by the same user is to associate them with some […]

Learn Huffman Encoding With Python

Lets walk through an implementation of huffman encoding and decoding in Python. For the purposes of demonstrating key ideas, I’m going to just treat bits as plaintext strings just to keep things simple. While this means that the output isn’t truly compressed as bytes, you will hopefully take away a deeper understanding of how it […]

Nand2tetris Python Assembler

Here’s my source code for the assembler for the nand2tetris HACK assembly language written in Python 3. This implementation emphasizes readability above all else. Therefore, there are more function calls than necessary and many parts of the implementation assume valid inputs. It has been tested to work with all files provided in the course. I […]