It's time to sit by the fire, grab some hot cider, and listen to a story. No, this isn't fanfiction. On second thought... for some of us, this a horror story. 👻 Don't worry. It ends on a good note, with some thoughts on how the API landscape has changed the way we design applications. Are You Afraid of the Dark? is Once upon a time, established software principles dictated a very simple model of delivering . We called it the 3-tier architecture, a self-describing little thing named before software vendors learned to influence human psychology with buzz words. line of business applications It made sense, a logical separation of concerns — as we say in design pattern books — and it reflected a big change that was already underway. Wait, how did we even get here? Let's take a joyride in the technobabble time machine! Data and logic were once colocated, situated on specialized , living a blissful life ignoring network partitions... while solving other incredibly difficult problems associated with this architecture. User interfaces were text-based and delivered to the business user via simple teletype terminals. Programming languages — like — were run close to the data layer — often a relational database like . This was really the start of the thin client pattern. mainframe hardware COBOL DB2 As time progressed, databases maintained the desire for single-machine consistency and availability. User interfaces were migrating from terminal emulators to more modern desktop (and eventually) Web experiences. This represented a conflict. How do we get mainframe data outside the terminal emulator? Part of this migration path involved moving logic out of the mainframe and into , often with VT100 compatible terminal emulators connecting directly with programming language APIs via libraries. application servers Okay, wait... isn't all of this very boring? Maybe. But that's a trait associated with line of business applications. 🙃 Boring is a long-term survival strategy for software architecture. Increasingly, logic had to move closer to the client and farther from the data. This brings us to the fundamental desire for the aforementioned 3-tier architecture. - Consumes logic produced by a Web or application server, carefully crafted to create the ugliest Web sites we've ever seen. Presentation tier - That darn application server. It's really this tier that spawned a new breed of Business Process Management software and integration tooling. Logic tier - Pick a favorite monolithic database: Oracle, MySQL, Microsoft SQL Server. Apologies if some of these names induce anxiety. Data tier Let's hold on to our britches because we're getting to the good part. Everything has changed . Scrubbing the timeline a bit, skipping past some difficult years — SOAP vs. XML-RPC, MongoDB vs. CouchDB — let's look at some motivating aspects to the latest cool kid architectures. 😎 From the perspective of multi-tiered application architecture, our human-facing interfaces are being driven by APIs. Based on Postman's , 49% of respondents said that . This is astronomical and represents an evolution that's been steadily growing around us. 2021 State of the API Report more than half of the organization's development effort is spent on APIs We have arrived at a place of with respect to business logic. We are just now ingesting the concept of API-First. There are benefits to putting , but that's a different campfire story. 🏕🔥 dumb connectors and smart components more smarts in the messages Application developers are now often specialized in front-end vs. back-end, with a few of us shifting contexts as full-stack developers. In retrospect, this was all inevitable. The success of the medium was indisputable. As a result, . And we all grew with it. the Web got smarter So what do we do with all these line-of-business applications as we move forward into solving new century problems? Well, as it turns out, Let's look at how this all fits together, how we've redefined the 3-tier architecture. API Gateways are the new VT100 terminal emulators. - Thick clients are all the rage. While our slick, new Web apps don't contain the business logic, they often contain quite a bit. Decisions are now made in the browser. Experience tier all - We are utilizing and iPaaS platforms to facilitate interaction between our new experience tier and the API data sources we've already built over the years. Experience APIs can be pieced together using façade and scatter-gather patterns in the gateway, backed by security, analytics, and message transformation. Integration tier API Gateways - CRUD APIs, database connections, message queues... If it can be accessed over the network, it can be accessed by an API Gateway. The database has become an implementation detail. Microservices have fortified this as the new reality. Data source tier Collaboration has never been more critical to achieving success in line-of-business applications. Learn some tips and tricks for how to deal with this in . Logic is now a vertically-oriented concern. 5 Developer Tips for Surviving API-First We only see more exploration here, as folks look to federation, microservices, and even micro-frontends to achieve a sweet-spot of modularity and centralized data source access when crafting application experiences. Does this resonate? It does for a lot of folks. Again, we are in a time of migration. How long will it last? Well, the VT100 emulators and mainframes are around, all these years later. still Transient technology, as it turns out, may never die. 🧟 Also published . here

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