Doug Tabuchi tabuchid

##Some apps to install before moving forward:

#System Design Cheatsheet

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

##Basic Steps

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?

	// Asynchronously loads UIImages from the given URLs, but throttles the loading
	// to keep memory and CPU usage sane.
	- (RACSignal )loadImagesAtURLs:(NSArray )imageURLs {
	// Map each URL to a signal of work. The result is a signal of work signals.
	return [[imageURLs.rac_signal
	map:^(NSURL *imageURL) {
	return [[[[NSURLConnection
	// Load the URL asynchronously.
	rac_sendAsynchronousRequest:[NSURLRequest requestWithURL:imageURL]]
	reduceEach:^(NSURLResponse response, NSData data) {

	/// Observes a run loop to detect any stalling or blocking that occurs.
	///
	/// This class is thread-safe.
	@interface GHRunLoopWatchdog : NSObject

	/// Initializes the receiver to watch the specified run loop, using a default
	/// stalling threshold.
	- (id)initWithRunLoop:(CFRunLoopRef)runLoop;

	/// Initializes the receiver to detect when the specified run loop blocks for