CODE NEVER LIES, BUT IT CAN CONTRADICT ITSELF. Some contradictions lead to those “How can that possibly work?” moments. In an interview, the principal designer of the Apollo 11 Lunar Module software, Allan Klumpp, disclosed that the software controlling the engines contained a bug that should have made the lander unstable. However, another bug compensated […]
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API DESIGN IS TOUGH, PARTICULARLY IN THE ENTERPRISE. If you are designing an API that is going to have hundreds or thousands of users, you have to think about how you might change it in the future and whether your changes might break client code. Beyond that, you have to think how users of your […]
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HE BUILD AS A “BIG BANG” EVENT in project development is dead. The architect, whether an application or enterprise architect, should promote and encourage the use of continuous integration methods and tools for every project. The term continuous integration (CI) was first coined by Martin Fowler in a design pattern. CI refers to a set […]
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ON ANY PROJECT THAT IS IN PRODUCTION (i.e., it has customers that are using it), there will come a time when a change must be made; either a bug needs fixing, or a new feature must be added. At that point there are two possible choices: you can take the time needed to “do it […]
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This basic pattern focuses on avoiding unnecessary network latency. Communication between nodes is faster when the nodes are close together. Distance adds network latency. In the cloud, “close together” means in the same data center (sometimes even closer, such as on the same rack). There are good reasons for nodes to be in different data […]
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Conway’s Law is an adage named after computer programmer Melvin Conway, who introduced the idea in 1968. It concerns the structure of organizations and the corresponding structure of systems (particularly computer software) designed by those organizations. In various versions, Conway’s Law states: · Organizations which design systems are constrained to produce designs which are copies […]
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This pattern focuses on how an application should react when a cloud service responds to a programmatic request with a busy signal rather than success. This pattern reflects the perspective of a client, not the service. The client is programmatically making a request of a service, but the service replies with a busy signal. The […]
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This primer introduces multitenancy and commodity hardware and explains why they are used by cloud platforms. Cloud platforms are optimized for cost-efficiency. This optimization is partially driven by the high utilization of services running on cost-efficient hardware that manifests as multitenant services running on commodity hardware. The decisions made in building the cloud platform also […]
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This essential pattern for loose coupling focuses on asynchronous delivery of command requests sent from the user interface to a back-end service for processing. This pattern is a subset of the CQRS pattern. The pattern is used to allow interactive users to make updates through the web tier without slowing down the web server. It […]
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This advanced pattern focuses on horizontally scaling data through sharding. To shard a database is to start with a single database and then divvy up its data across two or more databases (shards). Each shard has the same database schema as the original database. Most data is distributed such that each row appears in exactly […]
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The Eventual Consistency primer introduces eventual consistency and explains some ways to use it. This primer uses the CAP Theorem to highlight the challenges of maintaining data consistency across a distributed system and explains how eventual consistency can be a viable alternative. In an eventually consistent database, simultaneous requests for the same data value can […]
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Howard’s Law of Occult Game Design (or just The Law of Occult Game Design or Howard’s Law) can be expressed as a formula: “Secret Significance ? Seeming Innocence × Completeness.” Translated into everyday speech, this equation means that the power of secret significance is directly proportional to the apparent innocence and completeness of the surface […]
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