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Principal Engineer @Unacademy • Data @amazon • Platform @practo | Writes about Language internals, System Design, Programming and Math in Computer Science.

Bitcask is one of the most efficient embedded Key-Value (KV) Databases designed to handle production-grade traffic. The paper that introduced Bitcask to the world says it is a Log-StructuredHash Table for Fast Key/Value Data which, in a simpler language, means that the data will be written sequentially to an append-only log file and there will be pointers for each key pointing to the position of its log entry. …


One of the most important virtues of any distributed system is its ability to detect failures in any of its subsystems before things go havoc. Early detection of failures helps in taking preventive actions and ensuring that the system stays fault-tolerant. The conventional way of failure detection is by using a bunch of heartbeat messages with a fixed timeout, indicating if a subsystem is down or not.

In this essay, we take a look into an adaptive failure detection algorithm called Phi Accrual Failure Detection, which was introduced in a paper by Naohiro Hayashibara, Xavier Défago, Rami Yared, and Takuya…


Encryption is a process of encoding messages such that it can only be read and understood by the intended parties. The process of extracting the original message from an encrypted one is called Decryption. Encryption usually scrambles the original message using a key, called encryption key, that the involved parties agree on.

The strength of an encryption algorithm is determined by how hard it would be to extract the original message without knowing the encryption key. Usually, this depends on the number of bits in the key — bigger the key, the longer it takes to decrypt the enciphered data.


Iterables in Python are objects and containers that could be stepped through one item at a time, usually using a for ... in loop. Not all objects can be iterated, for example - we cannot iterate an integer, it is a singular value. The best we can do here is iterate on a range of integers using the range type which helps us iterate through all integers in the range [0, n).

Since integers, individualistically, are not iterable, when we try to do a for x in 7, it raises an exception stating TypeError: 'int' object is not iterable. So…


C language does not support inheritance however it does support Structure Compositions which can be tweaked to serve use-cases requiring parent-child relationships. In this article, we find out how Structure Compositions help us emulate inheritance in C and keep our code extensible. We will also find how it powers two of the most important things to have ever been invented in the field of computer science.

What is structure composition?

Structure Composition is when we put one structure within another, not through its pointer but as a native member — something like this

In the example above, we define a node of a linked…


The RUM Conjecture states that we cannot design an access method for a storage system that is optimal in all the following three aspects — Reads, Updates, and, Memory. The conjecture puts forth that we always have to trade one to make the other two optimal and this makes the three constitutes a competing triangle, very similar to the famous CAP theorem.

Access Method

Data access refers to an ability to access and retrieve data stored within a storage system driven by an optional storage engine. Usually, a storage system is designed to be optimal for serving a niche use case and…


Consistent hashing is a hashing technique that performs really well when operated in a dynamic environment where the distributed system scales up and scales down frequently. The core concept of Consistent Hashing was introduced in the paper Consistent Hashing and RandomTrees: Distributed Caching Protocols for Relieving Hot Spots on the World Wide Web but it gained popularity after the famous paper introducing DynamoDB — Dynamo: Amazon’s Highly Available Key-value Store.

Since then the consistent hashing gained traction and found a ton of use cases in designing and scaling distributed systems efficiently. The two famous examples that exhaustively use this technique…


An integer in Python is not a traditional 2, 4, or 8-byte implementation but rather it is implemented as an array of digits in base 2³⁰ which enables Python to support super long integers. Since there is no explicit limit on the size, working with integers in Python is extremely convenient as we can carry out operations on very long numbers without worrying about integer overflows. This convenience comes at a cost of allocation being expensive and trivial operations like addition, multiplication, division being inefficient.

Each integer in python is implemented as a C structure illustrated below.

It is observed…


Binary Search is an algorithm that finds the position of a target value in a sorted list. The algorithm exploits the fact that the list is sorted, and is devised such that is does not have to even look at all the n elements, to decide if a value is present or not. In the worst case, the algorithm checks the log(n) number of elements to make the decision.

Binary Search could be tweaked to output the position of the target value, or return the position of the smallest number greater than the target value i.e. …


Copy-On-Write, abbreviately referred to as CoW suggests deferring the copy process until the first modification. A resource is usually copied when we do not want the changes made in either to be visible to the other. A resource here could be anything — an in-memory page, a database disk block, an item in a structure, or even the entire data structure.

CoW suggests that we first copy by reference and let both instances share the same resource and just before the first modification we clone the original resource and then apply the updates.

Deep copying

The process of creating a pure clone…

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