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What is Difference Between Two-Tier and Three-Tier Architecture?

In my previous post I have outlined points to be considered while testing Web based applications. In today’s software testing class we are discussing about the Two-Tier and Three-Tier architecture.

All projects are broadly divided into two types of applications 2 tier and 3 tier architecture. Basically high level we can say that 2-tier architecture is Client server application and 3-tier architecture is Web based application. Below I am concentrating on the difference between Two-Tier and Three-Tier Architecture, what all advantages, disadvantages and practical examples.

Two-Tier Architecture:

The two-tier is based on Client Server architecture. The two-tier architecture is like client server application. 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.

Two-Tier Architecture

Two-Tier Architecture

The above figure shows the architecture of two-tier. Here the direct communication between client and server, there is no intermediate between client and server.

Let’s take a look of real life example of Railway Reservation two-tier architecture:

Let’s consider that first Person is making Railway Reservation for Mumbai to Delhi by Mumbai Express at Counter No. 1 and at same time second Person is also try to make Railway reservation of Mumbai to Delhi from Counter No. 2

If staff from Counter No. 1 is searching for availability into system & at the same staff from Counter No. 2 is also looking for availability of ticket for same day then in this case there is might be good change of confusion and chaos occurs. There might be chance of lock the Railway reservation that reserves the first.

But reservations can be making anywhere from the India, then how it is handled?

So here if there is difference of micro seconds for making reservation by staff from Counter No. 1 & 2 then second request is added into queue. So in this case the Staff is entering data to Client Application and reservation request is sent to the database. The database sends back the information/data to the client.

In this application the Staff user is an end user who is using Railway reservation application software. He gives inputs to the application software and it sends requests to Server. So here both Database and Server are incorporated with each other, so this technology is called as “Client-Server Technology“.

The Two-tier architecture is divided into two parts:

1) Client Application (Client Tier)
2) Database (Data Tier)

On client application side the code is written for saving the data in the SQL server database. Client sends the request to server and it process the request & send back with data. The main problem of two tier architecture is the server cannot respond multiple request same time, as a result it cause a data integrity issue.


  1. Easy to maintain and modification is bit easy
  2. Communication is faster


  1. In two tier architecture application performance will be degrade upon increasing the users.
  2. Cost-ineffective

Three-Tier Architecture:

Three-tier architecture typically comprise a presentation tier, a business or data access tier, and a data tier. Three layers in the three tier architecture are as follows:

1) Client layer
2) Business layer
3) Data layer

1) Client layer:

It is also called as Presentation layer which contains UI part of our application. This layer is used for the design purpose where data is presented to the user or input is taken from the user. For example designing registration form which contains text box, label, button etc.

2) Business layer:

In this layer all business logic written like validation of data, calculations, data insertion etc. This acts as a interface between Client layer and Data Access Layer. This layer is also called the intermediary layer helps to make communication faster between client and data layer.

3) Data layer:

In this layer actual database is comes in the picture. Data Access Layer contains methods to connect with database and to perform insert, update, delete, get data from database based on our input data.

Three-tier Architecture

Three-tier Architecture


  1. High performance, lightweight persistent objects
  2. Scalability – Each tier can scale horizontally
  3. Performance – Because the Presentation tier can cache requests, network utilization is minimized, and the load is reduced on the Application and Data tiers.
  4. High degree of flexibility in deployment platform and configuration
  5. Better Re-use
  6. Improve Data Integrity
  7. Improved Security – Client is not direct access to database.
  8. Easy to maintain and modification is bit easy, won’t affect other modules
  9. In three tier architecture application performance is good.


  1. Increase Complexity/Effort

This is the common Question asked in the Interview. Hope this article helped you understanding Two-Tier and Three-Tier Architecture with example.
Thanks and Happy Testing!!!

I think this will have an idea of two-tier and three-tier architecture. To get software testing articles in your inbox click here to Subscribe with your email address link. Also I would like all of you to please join this discussion and add more valuable points to it. Thanks.

49 comments to What is Difference Between Two-Tier and Three-Tier Architecture?

  • shweta

    Two tier basically comprise of Presentation and database layer wheresas in three tier these are segregated.

  • Rangnathan Reddy

    its very good for beginners….thanks

  • Test

    Simple and clear. Thanks You.

  • Sugnesh


  • aslam sharif

    Crest and clear to understand. I would certainly recommend it to my friends.


  • sajisharma

    Good informative post..!!

  • very informative and full of knowledge post. Usually people get stuck in to difference between two tier and 3 tier architecture

  • mohan

    its very useful me..

  • Dattatray Walunj

    Nice post, very useful…

  • senthil

    Clear and Easy to understand. Thanks a lot :)

  • Satish

    I think it’s short and simple…..thks…..

  • sivakoti

    Very nice and full informaction about 2 and 3 tires….

    Thanks for you

  • senthil

    very easy to understanding

  • Iqbal Mohammed

    Can you Please Explain Real life Example of Three tier architecture also…

  • vinodkumar


  • rahul chalkhure

    Easy to understand ,good bro

  • Bob Jones

    This website topics are really helpful. Keep writing!!

  • selva bharathi a

    its nice…very usefull. thanks

  • selva bharathi a


  • Rahul Talekar

    I need exact advantages of 3 tier over 2 tier architecture.


    It’s very easy to understand and helpful to me THANKS A LOT.

  • Sandeep

    Good info.

  • ajit kumar

    nice information for 2-tier and 3-tier

  • kiran

    why in DAL configurationManager is not allowing eventhough i
    wrote namespace of Data.

  • vivek chandra

    Simple and clear. Thanks You

  • raj chaturvedi

    good knowledge about 2-tier and 3-tier



  • Mukta

    It is really good. Can you name some Application Server? And,please tell me if Banking application is 3-tier application? My understanding from above explanation is Yes Reason being: All Customers information and account information,Amount Balance are kept in Data Source(3rd layer as per the example shown above).Front end is nodoubt is Presentation layer and where the transaction happens ( like, Transfer 50000 from Account A TO B ) is Business layer. Please correct me if am wrong in understanding.



  • Ian Smith

    It would have been useful to explain how the 3-tier model resolves the issue of the two ticket agents making simultaneous requests.

  • Ndumba Paulus

    Great post, now i can understand it better. Thanks

  • Amar Balikai

    very easy to understand and very use full it.thanks

  • Ramsingh Prajapati

    I love the way you explained, it is easy to understand the concepts
    Thank you

  • Ashwathi

    Simple and easy to understand….Thanks a lot….its really helpful for me….:-)

  • Ashish Porwal

    good knowledge and cleared the concept. Thanks a lot for sharing the details.

  • sharif hossen


  • urvi patel

    Nice post,provide more information of the both architecture

  • avani brahmbhatt

    Nice explanation….. Thanks a lot….. For Easy Understanding To Me…

  • Abdul Jaleel

    Really nice post,got a clear idea about both architecture now.Thank You…keep going.

  • GL

    Simply made to know.Tnks

  • Happy Jain

    Thank you.Very easy to understand.

  • Happy Jain

    Thank You.

  • Happy Jain

    Thank You

  • viral


  • Kimberly

    Thank you for the information. I am a student and this is new to me. Thanks for your help.

  • AFG

    The “What is Difference Between Two-Tier and Three-Tier Architecture?” was a useful information for me but I wanted to know a bout the author of this topic but unfortunately I couldn’t find the author, in-cause of not plagiarizing this topic, I wanted to cite the reference.

  • Shammi Aktar

    Very refreshing and knowledgeable for anyone.


  • sathiya

    i got clear idea about tier types , thank u very very much…….

  • Shivling Bodke

    Thanks for sharing article,
    Its simple to understand.

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