Prev Next

Erlang / Erlang Basics Interview questions

What is Mnesia?

Mnesia is Erlang's built-in distributed database, layered on top of ETS/DETS storage. Unlike ETS, Mnesia adds transactions, replication across nodes, and optional disk persistence, so multiple nodes in a cluster can share and safely update the same tables.

mnesia:create_table(person, [{attributes, record_info(fields, person)}]),
mnesia:transaction(fun() ->
    mnesia:write(#person{name = "Ada", age = 34})
end).

Because table rows are ordinary Erlang records/terms and queries are written in Erlang itself (or via mnesia:select/2 match specifications), there's no separate query language to learn the way SQL sits apart from application code.

It fits well for cluster-local configuration and session data where you want ACID-ish transactions without standing up an external database, though very large datasets or complex relational queries are usually better served by a dedicated external database.

What does Mnesia add on top of plain ETS tables?
How are Mnesia queries typically written?

More Related questions...

What is Erlang? What is the BEAM virtual machine? What are processes in Erlang? What is the actor model in Erlang? What are atoms in Erlang? What are tuples in Erlang? What are lists in Erlang? What is pattern matching in Erlang? Define immutability in Erlang? What is a PID? What is a module in Erlang? What are guards used for in Erlang? What is OTP? What is a gen_server? What is a supervisor? Describe the "let it crash" philosophy? What are records in Erlang? What is message passing? What is hot code loading? What are binaries/bitstrings in Erlang? What is ETS? What is Mnesia? What are list comprehensions? What is a behavior in Erlang? What are ports in Erlang? What is a NIF (Native Implemented Function)? How do you spawn a process in Erlang? How does Erlang achieve concurrency without shared memory? What is the difference between spawn and spawn_link? What is the difference between a list and a tuple? Why is Erlang considered fault-tolerant? How does pattern matching differ from equality comparison? When should you use ETS instead of process state? How do you handle errors in Erlang without try/catch? Why doesn't Erlang have mutable variables? What is the difference between gen_server and gen_statem? How do you implement a simple supervision tree? What happens when a linked process crashes? When would you choose Mnesia over ETS? How do you use the observer tool to inspect a running system? Explain the execution flow of a gen_server call? Explain the internal working of the BEAM scheduler? How can you optimize message passing between heavy processes? Explain the lifecycle of a supervised process? How do you troubleshoot process mailbox overflow? What is the difference between synchronous and asynchronous message passing in OTP? Which is better for state management, ETS or process dictionaries, and why? How does distributed Erlang handle node failures?
Show more question and Answers...

Erlang Advanced Interview questions

Comments & Discussions

Interviews Questions

About Javapedia.net

Javapedia.net is for Java and J2EE developers, technologist and college students who prepare of interview. Also this site includes many practical examples.

This site is developed using J2EE technologies by Steve Antony, a senior Developer/lead at one of the logistics based company.

Follow Javapedia updates

contact: javatutorials2016[at]gmail[dot]com

Kindly consider donating for maintaining this website. Thanks.

Copyright © 2026, javapedia.net, all rights reserved. · .

DMCA.com Protection Status