Example of 4-Tier (for N-Tier) Architecture?

Question

Recently a friend of mine asked me about N-Tier architectures and I was able to explain to him about 1, 2 and 3 tier architectures with examples. But I was stuck when I wanted to give examples for more than 3 tiers. I googled and binged for help, but could not find any decent examples.

The fact that it is named N-tier makes me think that 'N' can be any number starting from 1. But I couldn't find any examples for 4 or 5 tier.

Can somebody share some examples of N-tier architectures that involves more than 3 tiers?

Answer 1

1. Fundamental Services : e.g. Database, Directory Services, File & Print Services, Hardware abstraction. This tier is increasingly called the platform.
2. Business Domain Tier : An Application Server such JavaEE including EJB, DCOM or CORBA Service Objects. Provide business functionality, increasing using SOA and Micro-services.
3. Presentation Tier : e.g. Java Servlets/JSP, ASP, PHP. This tier will increasingly include WebServices as proxies and adaptors for business tier services.
4. Client Tier : Thin clients like HTML Pages on Browsers and Rich Clients like Java WebStart & Flash.

• In Java EE it is common to divide the Business Domain tier into Data-Access (Entity Beans) & Business Services (Session Beans).
• In an Enterprise SOA (Service Oriented Architecture) the ESB (Enterprise Service Bus) would typically exist as an additional tier between tiers 1 & 2. It may be part of the platform provision.
• In Mashups you could have an aggregation tier between tier 3 & 4.

The move to being called N-Tier is a reflection of the move to increasingly componentised architectures from the older client-server to first 3-Tier then 4-Tier. The defining characteristic of a tier is a clearly defined interface with a separation of concerns.

Answer 2

Five minutes ago I've read an article of this https://www.nginx.com/blog/time-to-move-to-a-four-tier-application-architecture

Client is where you read it Api or your application back-end is where you assemble it .. Data aggregation.. Either goes through the jsons/xmls from outsourced things or queries on your database and lastly service tier is where you actually do the query on database or run function on big data or read GPS locations and maps from google ... That is how I see it in this case. It simply divided the data layer from three tier.

But this N-tier model is totally abstract so you can tear your infrastructure until you have some logically atomic parts only. Still dividing the previous structure.