Design an In-Memory Key-Value Store | Machine Coding Round Questions (SDE II/III)

Problem Statement : https://workat.tech/machine-coding/practice/design-key-value-store-6gz6cq124k65

Video Solution : https://youtu.be/SGtd--4WdLA

Problem Statement Design an In-Memory Key-Value Store like Redis.

Requirements

The key-value store will be in-memory and does not require access to the file system. The key will always be a string. The value would be an object/map. The object would have attributes and corresponding values. Example => "sde_bootcamp": { "title": "SDE-Bootcamp", "price": 30000.00, "enrolled": false, "estimated_time": 30 } Each attribute key would be a string and the attribute values could be string, integer, double or boolean. The key-value store should be thread-safe. The Key-Value store should expose the following functions: get(String key) => Should return the value (object with attributes and their values). Return null if key not present search(String attributeKey, String attributeValue) => Returns a list of keys that have the given attribute key, value pair. put(String key, List<Pair<String, String>> listOfAttributePairs) => Adds the key and the attributes to the key-value store. If the key already exists then the value is replaced. delete(String key) => Deletes the key, value pair from the store. keys() => Return a list of all the keys The value object should override the toString method to print the object as a comma-separated list of key-value pairs for the attributes. Example: attribute1: attribute_value_1, attribute2: attribute_value_2, attribute3: attribute_value_3 The data type of an attribute should get fixed after its first occurrence. Example: Once we encounter an attribute age with an integer value then any entry with an age attribute having a non-integer value should result in an exception. Nothing should be printed inside any of these methods. All scanning and printing should happen in the Driver/Main class only. Exception Handling should also happen in the Driver/Main class. Input/Output Format The code should strictly follow the input/output format and will be tested with provided test cases.

Input Format

Multiple lines with each line containing a command.

Possible commands:

get put .... delete search keys exit Stop taking the input when you encounter the word exit.

Assume that attribute keys and values would not have space in between.

Output Format

Print output based on the specific commands as mentioned below.

get Comma and space-separated attributes. Example:

attribute1: attribute_value_1, attribute2: attribute_value_2, attribute3: attribute_value_3 Print "No entry found for " if get returns null.

put Do not print anything. Print "Data Type Error" if attribute has data type other than previous set.

delete Do not print anything.

search Comma-separated keys. Example:

key1,key2,key3,key4 Print in sorted order

keys Comma-separated keys. Example:

key1,key2,key3,key4 Print in sorted order

Example

Sample Input

put sde_bootcamp title SDE-Bootcamp price 30000.00 enrolled false estimated_time 30 get sde_bootcamp keys put sde_kickstart title SDE-Kickstart price 4000 enrolled true estimated_time 8 get sde_kickstart keys put sde_kickstart title SDE-Kickstart price 4000.00 enrolled true estimated_time 8 get sde_kickstart keys delete sde_bootcamp get sde_bootcamp keys put sde_bootcamp title SDE-Bootcamp price 30000.00 enrolled true estimated_time 30 search price 30000.00 search enrolled true

Expected Output

title: SDE-Bootcamp, price: 30000.00, enrolled: false, estimated_time: 30 sde_bootcamp Data Type Error No entry found for sde_kickstart sde_bootcamp title: SDE-Kickstart, price: 4000.00, enrolled: true, estimated_time: 8 sde_bootcamp,sde_kickstart No entry found for sde_bootcamp sde_kickstart sde_bootcamp sde_bootcamp,sde_kickstart

Expectations

Make sure that you have a working and demonstrable code Make sure that the code is functionally correct Code should be modular and readable Separation of concern should be addressed Please do not write everything in a single file (if not coding in C/C++) Code should easily accommodate new requirements and minimal changes There should be a main method from where the code could be easily testable [Optional] Write unit tests, if possible No need to create a GUI