The Hekaton is a new database engine, also known as SQL Server In-Memory OLTP.
Hekaton collaborated with Microsoft Research and released with Microsoft SQL Server 2014.

The Hekaton is a Greek word and meaning is 100 because that newly launched in-memory database which is 100 times faster than the existing SQL Server engine.

If you don’t know about In-memory database, you can visit a below article.

Database Theory: What is In-memory Database?

If we look at traditional RDBMS system, memory resources are expensive, and mostly optimize for disk storage.

The Hekaton allows us to work with memory-optimized tables and indexes which entirely stores in the main memory, and still, we can access via T-SQL like any other regular tables.

We can also create a stored procedure by adding the “WITH NATIVE_COMPILATION” clause that only refers to the memory-optimized tables.

The Hekaton eliminates logical locks using automatic SNAPSHOT ISOLATION with multi-versioning, also having a lock free and latch free structures for accessing the data.

How Hekaton is different than SQL Server standard relational engine?

Very simple answer,

SQL Server standard relational engine developed basically for those data which resides on disk, and it reads and writes 8 KB per data pages which are available in the extents. This process requires lots of CPU I/O and memory internal operations.

With the memory-optimized tables, there are no any data pages and extents. It stores only the data rows into memory with index pointer.

The engine also supports MVCC (Multiversion Concurrency Control) in which same data row has may be the different versions at a time so last updated version accessible by last most requests.

Because of MVCC nature, reader and writer process never block to each other in the Hekaton engine.

What is Multi Version Concurrency Control (MVCC)