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Master Crystal.

Crystal

Crystal mastery exercises. Become your team's resident Crystal expert.

97 exercises

Crystal

Crystal Challenges

Put your Crystal skills to the test. Practice by building popular open-source tools from scratch.

Build your own Redis

Build your own Redis

Discover concurrent programming in Crystal while also learning about TCP servers, network programming, and the Redis Protocol.

Respond to PING

Respond to multiple PINGs

Handle concurrent clients

Implement the ECHO command

Implement the SET & GET commands

Lists

Append an element

Append multiple elements

List elements (positive indexes)

List elements (negative indexes)

Prepend elements

Query list length

Remove an element

Remove multiple elements

Blocking retrieval

Blocking retrieval with timeout

Streams

The TYPE command

Create a stream

Validating entry IDs

Partially auto-generated IDs

Fully auto-generated IDs

Query entries from stream

Query single stream using XREAD

Query multiple streams using XREAD

Blocking reads without timeout

Blocking reads using $

Transactions

The INCR command (1/3)

The INCR command (2/3)

The INCR command (3/3)

The MULTI command

The EXEC command

Empty transaction

Queueing commands

Executing a transaction

The DISCARD command

Failures within transactions

Multiple transactions

Replication

Configure listening port

The INFO command

The INFO command on a replica

Initial replication ID and offset

Send handshake (1/3)

Send handshake (2/3)

Send handshake (3/3)

Receive handshake (1/2)

Receive handshake (2/2)

Empty RDB transfer

Single-replica propagation

Multi-replica propagation

Command processing

ACKs with no commands

ACKs with commands

WAIT with no replicas

WAIT with no commands

WAIT with multiple commands

RDB Persistence

RDB file config

Read a string value

Read multiple keys

Read multiple string values

Read value with expiry

Pub/Sub

Subscribe to a channel

Subscribe to multiple channels

Enter subscribed mode

PING in subscribed mode

Publish a message

Deliver messages

Sorted Sets

Create a sorted set

Retrieve member rank

List sorted set members

ZRANGE with negative indexes

Count sorted set members

Retrieve member score

Remove a member

Geospatial Commands

Respond to GEOADD

Validate coordinates

Store a location

Calculate location score

Respond to GEOPOS

Decode coordinates

Calculate distance

Search within radius

Authentication

Respond to ACL WHOAMI

Respond to ACL GETUSER

The nopass flag

The passwords property

Setting default user password

The AUTH command

Enforce authentication

Authenticate using AUTH

Many more to come...

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RECENT ACTIVITY 0

“ The Redis challenge was extremely fun. I ended up having to read the Redis Protocol specification doc pretty carefully in its entirety! The result felt like lightly-guided independent study, if that makes sense. (Which, again, was lots of fun)

Charles Guo Software Engineer, Stripe “ I think the instant feedback right there in the git push is really cool. Didn't even know that was possible!

Patrick Burris Senior Software Developer, CenturyLink