Test your Technical knowledge – Scenarios

  1. What is Internet of Things? Explain about any one of your recent work?
  2. Design DVD selling Software
  3. Design task scheduler for which cannot run when not running others scheduler
  4. how can you rollout certain functionality for only certain users?
  5. how do you design cab service application? What are the important functionalities needed?
  6. Design plumbing service – what are the basic functionalities needed?
  7. Suppose you have extremely large input data file to process, give the various options to process it? This was batch and input data file processing oriented question. Specific questions on batch based application design.
  8. Your application gone through the entire test phases and passed all gating criteria but in production now it is extremely slow. Business is looking for you to quickly act. What all the things your will do?
  9. How do you perform Code review for DAO?
  10. What is Capacity Planning? How do you perform?, What formula or technique you use to predict production infrastructure?
  • we determine load on system and based on historical data and expect judgment to extrapolate it.
  • complex scenario…saying I give you one high end sun Solaris machine, 64 gig ram….tell me how many concurrent user it will handle….basic formula
  • draw architecture for only those component which you design and propose in your last application……

Capacity Calculation


  1. Total users
  2. Page per view
  3. Total Page view in Peak = Total users * Page per view
  4. Page view per secs = Total users * Page per view/no of working day * 3600

5.Hits per sec = Page view per secs * 140


Work Load Characterization Values Notes


Total Visitors in Peak Time Window (PTW): 25000.0

Total Page views in Peak Time Window :100000.0

Number of working days in a month 21.0

Number of Seconds in PTW : 3600

Seconds in PTW = PTW in Hours x 3600

Page Views per second during PTW 30.0 Page views per second in PTW =

Total pages viewed in PTW / Seconds in PTW

Hits per second during PTW 4200 Page views per second in PTW * Number of Hits per Page (140)

CPU Time in ms per CPU/sec 1,000

Available CPU ms/sec per CPU 800 Based on 80% Utilization

CPU per Dynamic Portion of Page [ms] 120 (Based on 2.2 GHz Intel Xeon Processor (Standard))

CPU per Image Portion of Page [ms] 20 (Based on 2.2 GHz Intel Xeon Processor (Standard))

Total Web Server CPU Usage for Dynamic View [ms] 3600 (Page views per second in PTW * CPU per Dynamic Portion of Page [ms])

Total Web Server CPU Usage for Images [ms] 600 (Page views per second in PTW * CPU per Image Portion of Page [ms])

Total Combined CPU Usage for Dynamic Views and Images [ms] 4200 (CPU Usage for Dynamic Portion + CPU Utilization for Images)

40% CPU Overhead for SSL [ms] 1680 (Using SSL on Web Server Only)

System CPU Utilization [ms] 200 (Multiplexing, Job Scheduling, Application Threading Characteristics, etc.)

Total CPU Utilization [Web + Image + SSL + System] 6080

N  =  ( R + Z )  *  X

Where, N = Number of users

R = average response time (now you know, it can be pacing too)

Z = Think Time

X = Throughput (i.e. TPS)

Example, If N = 100, R = 2 sec, 100= (2+Z)*X and hence –> If Z=18, X = 5

I/O bound (DB Read, or reads a file, or gets the info from network) and CPU bound(like image processing or doing calculations)



  1. When you do code review for Spring, what are the key thing you look for…..Code review for Spring

instance variables and verify we don’t have data holders defined at class level…………………… if the code is

already in production and today you found there many such bean which has class level member data holders…..how you will communicate business on code change….because

business has so far not found this causing any problem in production?

Reference: Class level variable make thread safety issue for singleton bean


  1. Scenario 1) User is coming on application but either closing app or application is getting error out…how you still maintain data in system and take it forward.

Caching, messaging queue

  1. Scenario 2) Some of your services are not available, what you do to handle such scenarios?

fail safe approach – graceful exit

fault tolerant – allows system to work with same performance

  1. Scenario 3) In a workflow half of the operations are done but it partially failed in few systems in a distributed environment. How to do rollback in such distributed and multiple application integration scenarios?
  2. What is the problem Hadoop – MapReduce paradigm is solving?

Suited for loosely coupled parallelization tasks. Anything that involves doing operations on a large set of data, where the problem can be broken down into smaller independent sub-problems who’s results can then be aggregated to produce the answer to the larger problem.

  1. What if you don’t have caching framework? can you write your own…. draw a high level design for all the methods you need to write to

reload, refresh, cleanup and other tasks.

  1. How you determine memory bottlenecks in your application?

Read Heap Dump – Heap Dump is snapshot of object memory in heap

Look at largest size objects and analysis

Thread Dump -Snapshot of all the Threads in applications, need to be collected during application slow. It provide Thread ID, statuses, For analysis look for blocked and long running threads and based on ID , we can find code.

  1. What all Java built in feature you have used?
  2. If you want to build a scalable application, what all points you need to consider in application code?

static vs dynamic data separation

stateless, headless service

token based authentication




  1. What are the most critical challenges you faced in your last project?
  2. Why did you use specific data model?
  3. How do you evaluate a framework?

Analysis Business Need,


Type of Framework


  1. Finding memory, performance, security and size of codebase
  2. Design well defined SAAS Based system





  1. design online instance messaging system
  2. Decide Type of Architecure( Centralised vs Peer to Peer)
  3. Protocol(websocket – xmpp)

3.Security – Encryption etc…

  1. Location detection – Rooster
  2. Servers – Types of service – Increase number of servers

Online Video Streaming

1.Raw Video 2. Compression 3. encode 3. store 4.



  1. how online video streaming works?
  2. NFR related with provided solution
  3. Tell about scenario where you chose different technologies
  4. Patterns
  5. tell about your recent accomplishments
  6. Challenging Project most dynamic and impactful continuous integration project
  7. complete tech flow ecommerce on AEM
  8. Essential things to be followed on API design
  9. Stability and consistency (version)
  10. Flexibilty
  11. Security

Whitelisting the method

Secure against CSRF

Validate access to resources

Validate all input

  1. Easy adoption

Reference Link: http://www.toptal.com/api-developers/5-golden-rules-for-designing-a-great-web-api

  1. various search engine
  2. POC with details –
  3. what are the factors considered while choosing any product?
  4. any 3 achievement done in the project
  5. Influence Team Members
  6. How payment system works?
  7. Design Payment, Payroll system?

Hints: Consumer applications

Provider application

Handshake between Producer and Consumer

Varioius Integrations

Building Blocks for Provider applications



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