• Replication: Neo4j does allow writing through slaves, even then that’s being written to syncs with the master before returning to the client (writing through slaves works slower then writing directly to the master)
• Buffer writes using queues: this technique can be used in a high write load scenarios, in order to reduce contention. It enables to pause write operations without refusing client requests during maintenance periods.
• Global Clusters: Latency introduced by the physical separation of the regions can sometimes disrupt the coordination protocol. It is better to restrict master reelection by create slave-only databases
• Neo4j cluster, the full graph is replicated to each instance in the cluster

In order to avoid pitfalls we have to check the design for queryability

• Describe the client or end-user goals that motivate our model
• Rewrite these goals as questions to ask of our domain
• Identify the entities and the relationship that appear in these questions
• Translate these entities and relationships into Cypher path expressions
• Express the questions we want to ask of our domain as graph patterns using path expressions similar to the ones we used to model the domain

In this blog I will try to explain quickly what is a graphdb and how to eat it. First lets answer the question what is a Graph? A graph is a collection of vertices and edges (Say it little simpler graph is a set of nodes and the relationships that connect them)

Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position. Return the max sliding window.

Alembic is a lightweight database migration tool for usage with the SQLAlchemy Database Toolkit for Python.

Original idea of Circuit Breaker comes from electronic engineering where it comes in a form of automatic switch that designed to protected electrical circuit from damage by excess of current in the circuit.

Very interesting and confusing thing happens when we try to use resilience4j circuit-breaker and retry core modules together. Because both of them have fallback functionality, and it is very easy to get confused how to use it. if you configure wrong the following things may happen:

Sometimes we may need to override build functionality of lombok builder. It could be helpful to avoid additional call of some functionality after calling build(). Here is the example of usage:

Gatling is another trendy stress-test tool, which can be used for simple scenarios, as well as for complex scenarios. Quick start tutorial can be followed from here

Amazon Athena is an interactive query service that makes it easy to analyze data in Amazon S3 using standard SQL. Athena is a serverless infrastructure that allows us to run SQL on S3 files. Athena helps to analyze unstructure, semi-structured and structured data stored in Amazon S3 (such as CSV, JSON, columnar data formats, Apache Parquet, Apache ORC). Detail references can be read from official aws web-page