Two-Tier Architecture And Three-Tier Architecture

Difference Between Two-tier Architecture and Three-Tier Architecture in Tabular Form

S.No	Comparison	Two-tier Architecture	Three -tier Architecture
1.	Diagram
2.	Architecture Type	Client -Server Architecture	Web -based application
3.	Working	Client will hit request directly to server and client will get response directly from server,The direct communication takes place between client and server. There is no intermediate between client and server. Because of tight coupling a 2 tiered application will run faster.	Here in between client and server middle ware will be there, if client hits a request it will go to the middle ware and middle ware will send to server and vice versa.
4.	Layers	2-tier means Design layer/Client Application (Client Tier) Data layer/Database (Data Tier)	3-tier means Design layer /presentation Business layer or Logic layer / data access tier Data layer / data tier.
5.	Security	Less secured as client can talk to database directly	Highly secured as client is not allowed to talk to database directly
6.	Scalability	Poor	Excellent as requests can be load balanced between servers
7.	Reusability	Mostly clients are monolothic and thereby reusability not possible	Reusability more with services implementation
8.	Advantages:	Easy to maintain and modification is bit easy. Communication is faster.	Better Re-usability. Improve Data Integrity. Improved Security – Client is not direct access to database. Forced separation of user interface logic and business logic. Business logic sits on small number of centralized machines (may be just one). Easy to maintain, to manage, to scale, loosely coupled etc.
9.	Disadvantages:	In two tier architecture application performance will be degrade upon increasing the users. Cost-ineffective.	Increase Complexity/Effort