Saswata Dutta saswata-dutta

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

This gist contains lists of modules available in

Python 3.10
Python 3.9
Python 3.8
Python 3.7
Python 3.6
Python 2.7

in AWS Lambda.

What the hell are environment variables?

They're just variables you set on your system that various programs/processes can read. A fairly standard example in javascript circles would be setting your NODE_ENV variable to "production" or "development", altering how node code is executed on your system (for example showing more debug messaging when in development).

With most shells there's a way to set them for the current session, and a way to set them for all sessions. The following is meant to be a guide on how to set env vars in the various shells.

Bash (The default shell on OSX)

Setting for the session:

Go to https://developer.apple.com/downloads/index.action and search for "Command line tools" and choose the one for your Mac OSX
Go to http://brew.sh/ and enter the one-liner into the Terminal, you now have brew installed (a better Mac ports)
Install transmission-daemon with
```
brew install transmission
```

Copy the startup config for launchctl with

ln -sfv /usr/local/opt/transmission/*.plist ~/Library/LaunchAgents

	// ...
	Request request = new Request.Builder()
	.url(url)
	.tag(TAG)
	.build();

	// Cancel previous call(s) if they are running or queued
	OkHttpUtils.cancelCallWithTag(client, TAG);

	// New call

	package org.codefx.lab.stream;

	import java.util.Collection;
	import java.util.Objects;
	import java.util.Optional;
	import java.util.function.BinaryOperator;
	import java.util.function.Supplier;

	/**
	* Finds a certain customer in a collection of customers.

	import com.google.common.cache.CacheBuilder;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;
	import org.springframework.cache.CacheManager;
	import org.springframework.cache.annotation.CachingConfigurer;
	import org.springframework.cache.annotation.EnableCaching;
	import org.springframework.cache.guava.GuavaCache;
	import org.springframework.cache.interceptor.CacheErrorHandler;
	import org.springframework.cache.interceptor.CacheResolver;
	import org.springframework.cache.interceptor.KeyGenerator;

	/**
	* Fancy ID generator that creates 20-character string identifiers with the following properties:
	*
	* 1. They're based on timestamp so that they sort after any existing ids.
	* 2. They contain 72-bits of random data after the timestamp so that IDs won't collide with other clients' IDs.
	* 3. They sort lexicographically (so the timestamp is converted to characters that will sort properly).
	* 4. They're monotonically increasing. Even if you generate more than one in the same timestamp, the
	* latter ones will sort after the former ones. We do this by using the previous random bits
	* but "incrementing" them by 1 (only in the case of a timestamp collision).
	*/

	#include <string>
	#include <functional>

	using namespace std;

	template <typename T>
	struct Maybe{
	T just;
	bool isNothing;
	};

	import javax.persistence.EntityManager;

	import com.google.inject.AbstractModule;
	import com.google.inject.Inject;
	import com.google.inject.Singleton;
	import com.google.inject.persist.PersistService;
	import com.google.inject.persist.jpa.JpaPersistModule;

	public class DatabaseModule extends AbstractModule {