Here is the proven method on how to become a Redis Certified Developer in just a few days, using only the Redis online documentation and high-quality practice tests.
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Redis Certified Developer Program
Redis is still by far the most popular key-value store database, several times more popular than DynamoDB, Azure Cosmos DB or Memcached:
Most cloud vendors offer a fully managed Redis-based service, most often used for an in-memory cache:
The Redis certification program was launched in Nov 2019, with one single exam and certification. First step is to register for free for the Redis Certified Developer Program on the Redis University website. Redis University is a department of Redis Labs, the current maintainers of Redis.
Their main free resources include a Study Guide, and a free online practice test with 33 interactive questions. You can also enroll in some free courses, if you have enough time at your disposal and if they are available during your time period. The three courses recommended for the Redis exam are:
- [RU101] Introduction to Redis Data Structures
- [RU202] Redis Streams
While their courses could be excellent, I’ll rather not recommend them here, if you have only 3-4 days to prepare. You must however go over the Study Guide in detail, as your self-help will come mostly from:
- the excellent Redis online documentation
- Redis Best Practices
- a few other external blog articles referenced by the Study Guide
Yes, this is all you need. The exam is focused in particular on Data Structures and Data Modeling, and you’ll have to learn in detail most of these Redis commands in the first two days.
How to Prepare in Just 3 Days
The Study Guide divides everything into the following categories or domains:
- General Redis Knowledge – with computational complexity and Big-O notation, persistence options in Redis, Redis Enterprise, main Redis modules and Redis-CLI.
- Redis Keys – with KEYS vs SCAN, DEL vs UNLINK, TTL and expire time.
- Data Structures – deep dive into strings, bitfields and bitmaps, lists, hashes, sets and sorted sets, streams, geospatial indexes, HyperLogLog, Pub/Sub. Learn about Redis transactions and Lua scripts, pipelining and a few other internals.
- Data Modeling – completes the previous chapter with specific applications from combinations of Redis commands using specific structures. Learn how to generate unique IDs, create different queue types, index data in Redis, count and map relationships.
- Debugging – learn about OBJECT, TYPE, MONITOR, INFO commands. Understand the Redis-specific RESP protocol.
- Performance and Correctness – with memory usage and eviction policies, and more on transactions, Lua scripts and pipelining.
- Clustering Concepts – with hash tags and hash slots, and allowed/disallowed multi-key operations when using shards. Understand how a cluster splits and spreads data on multiple nodes.
Day 1. After a brief introduction to Redis, if you don’t already know what it does, take your time to go over all primary built-in data types or data structures, understand what they are and what they do, and what kind of controllers they are best suited for.
More than 60% of all exam questions are related directly to Data Structures and Data Modeling. While Data Structures is mostly about knowledge, and their well structured online documentation is the best resource you may find, Data Modeling is more like an art, it’s about deeper understanding on how to use previous building blocks for specific use cases. Lots of questions involving sorted sets, and 2-3 questions on specific bitmap/bitfield commands.
Day 2. Continue with Data Structures and Data Modeling, diving deeper into the “modeling” part. Take your time to properly understand Redis transactions, Lua scripting and pipelining.
Go back to the Big-O notation and quickly review your Computer Science notes, because you will have plenty of questions (5-8) on comparing or estimating some O(log(n)) or O(n) internal Redis algorithms. Understand why most count-related or element-based operations are O(1), and most range commands are O(n). Carefully consider all specific and interesting use cases from the Study Guide.
Day 3. Spend half a day to cover the operations-related and administration chapters, the stuff about debugging, performance and clustering. Understand persistence options, deployment types, eviction policies (2-3 questions will be on them). Understand RESP and the few text-based conventions for passing arrays and bulk strings to the server.
But do not waste too much on replication, configuration and the redis-cli syntax, because you’re likely have close to no questions on them.
Redis Certified Developer Practice Tests
Day 4. Use the rest of Day 3 and the Day 4, right before your scheduled exam, to intensively play with practice exams, again and again, until you consistently score above 90% on each.
After the Study Guide, there is a free online practice test with 33 questions, divided into 3 modules or parts. Get very familiar with it, because chances are some of these questions will appear in the final exam. Also, you will have the exact same format for the online exam, as it will be hosted into the same portal.
What I did, to be able to practice again and again on the same set, before the exam, is I created and logged in with two other user accounts. Now problem is at the actual exam you will get redirected to the same portal, with a new exam package. Mine was nowhere to be found, because I was logged in automatically with a different user account. Until I figured out, with the proctor, that I had to log out and back in, with my first account.
Before the exam, make sure you are logged in at the Redis University portal with the same account you used to book the exam!
The 33 questions exposed here before are not enough. For my other IT certification exams I used to regularly spend some $10-$15 bucks on bulk practice tests, with dozens or hundreds of similar exam questions (not dumps!) from Udemy, or Kindle ebooks. I didn’t find any good practice tests when I passed this exam. But I later created mine, to help you now with a better choice.
My brand new Become a Redis Certified Developer: Practice Exams course on Udemy has two original practice tests, with 80 questions each, exactly like the real exam. All questions present 4 choices, closely emulating the ones from the real exam. They come up with detailed answers and explanations, so you’ll be also able to learn (a lot) by just looking at the answers. I also included as bonus the Redis University practice test, to be able to use it again and again without being forced to create each time a new account.
An alternative is my brand new Redis Certified Developer: Exam Practice Tests ebook on Amazon, with the same 160 total questions, but in Kindle format.
I know it’s self-promotion, but I could almost guarantee my practice exams will help you so much! If last day you just take the time to relax, and play again and again with these practice tests, I could almost say that a consistent 90% on these tests will help you pass the Redis Certified Developer exam with 80% or more.
Redis Certified Developer Exam
The proctored exam has 80 questions, with 4 choices each. Most of them are single-choice, a few only (4-5) with multiple selections. There are no simple True/False questions. There will be 8 modules or pages, with 10 questions per page, each question with its own Submit button, very similar to the free practice test.
You’ll have a time limit of 90 minutes, and this may sound not enough. However, if you prepared well, you’ll be able to spend just a few seconds on most of the questions. You should worry more to not lose focus, because 80 questions are a lot. After a few minutes you may realize you barely answered a dozen of them, so you’ll have to remain concentrated.
There are 700 total points for this exam, and you must get at least 500. This means the passing score is around 72%, and you’re allowed to get wrong less than 22 questions overall.
The exam costs $120 US, that you must pay though ProctorU. Unlike other proctored IT certification exams, this one will require to install a ProctorU Chrome extension. Reserve at least three days in advance, and beware there is only one week every month when tests are available. For instance, next three exam windows for 2020 are between Sep 15 .. Sep 22, Oct 13 .. Oct 19, Nov 10 .. Nov 16.
To me, this was costly. I think I got wrong 4-5 questions related to the same structure and Redis command, which I assumed an incorrect order for parameter passing. I figured out only close to the end the order was different, but I couldn’t go back to change my answers.
For any question, remember that when you click Submit this was your final answer! Try also to review and remember the exact syntax for most popular Redis commands.
You don’t get the results right away. You have to wait for the exam window to close, and spend up to two weeks until you know how you did. I was lucky to get my results in just two days, because I used the last day of my exam window.
If you pass, you get an email with your score and the percentage for each category. A badge and a certificate will be sent to you later on. This certificate does not expire, it’s for life!
To conclude, it is so much fun to prepare for the Redis Certified Developer exam. It’s also feasible to prepare in just a few days. I truly prepared in less than four days, with very little previous knowledge about Redis, about all the internals required for this exam.
Beware however this is not a walk in a park, and I did not get the best score with my marathon. Using just a few days to prepare doesn’t make you a Redis expert. I just hope the few tricks I shared here, and the practice tests I prepared, will help you do better. Good luck!