Erlang is a functional programming language developed by Ericsson for use in telecom applications. Because they felt that it’s unacceptable for a telecom system to have any significant downtime, Erlang was built to be (among other things):

  • distributed and fault-tolerant (a piece of failing software or hardware should not bring the system down)
  • concurrent (it can spawn many processes, each executing a small and well-defined piece of work, and isolated from one another but able to communicate via messaging)
  • hot-swappable (code can be swapped into the system while it’s running, leading to high availability and minimal system downtime)


Erlang makes heavy use of recursion. Since data is immutable in Erlang, the use of while and for loops (where a variable needs to keep changing its value) is not allowed.

Here’s an example of recursion, showing how a function repeatedly strips the first letter from the front of a name and prints it, only stopping when the last letter has been encountered.



print_name([RemainingLetter | []]) ->
  io:format("~c~n", [RemainingLetter]);
print_name([FirstLetter | RestOfName]) ->
  io:format("~c~n", [FirstLetter]),


> name:print_name("Mike").

There is also a heavy emphasis on pattern-matching, which frequently eliminates the need for an if structure or case statement. In the following example, there are two matches for specific names, followed by a catch-all for any other names.



say_hello("Mary") ->
  "Welcome back Mary!";
say_hello("Tom") ->
  "Howdy Tom.";
say_hello(Name) ->
  "Hello " ++ Name ++ ".".


> greeting:say_hello("Mary").
"Welcome back Mary!"
> greeting:say_hello("Tom").
"Howdy Tom."
> greeting:say_hello("Beth").
"Hello Beth."

Erlang Term Storage

Erlang Term Storage, normally abbreviated as ETS, is an in-memory database built into OTP. It’s accessible within Elixir, and is a powerful alternative to solutions like Redis when your application runs on a single node.

Quick Start

To create an ETS table you first need to initialize a table tableName =, []), once you have initialized a table you can: insert data, lookup values, delete data, and more.

ETS Demo in IEX

iex(1)> myETSTable =, [])
iex(2)> :ets.insert(myETSTable, {"favoriteWebSite", "freeCodeCamp"})
iex(3)> :ets.insert(myETSTable, {"favoriteProgrammingLanguage", "Elixir"})
iex(4)> :ets.i(myETSTable)
<1   > {<<"favoriteProgrammingLanguage">>,<<"Elixir">>}
<2   > {<<"favoriteWebSite">>,<<"freeCodeCamp">>}
EOT  (q)uit (p)Digits (k)ill /Regexp -->


ETS Tables are not persistent and are destroyed once the process which owns it terminates. If you would like to store data persistently a traditional database and/or file-based storage is recommended.

Use cases

ETS Tables are commonly used for caching data in the application, for example account data fetched from a database may be stored in an ETS Table to reduce the amount of queries to the database. Another use case is for rate limiting use of features in a web application - ETS’s fast read and write speed make it great for this. ETS Tables are a powerful tool for developing highly concurrent web applications at the lowest possible hardware cost.

Try it out

There are websites where you can try running Erlang commands without having to install anything locally, like these:

If you’d like to install it on your (or a virtual) machine, you can find installation files at or on Erlang Solutions.

More Information: