Book · 2019
Database Internals
by Alex Petrov
Alex Petrov walks you through B-trees, LSM storage, and Paxos at a pace that doesn't assume you've already read the Spanner paper.
What does Reddit think of Database Internals?
Seven mentions in seven years is thin, and almost every one of them shows up in the same sentence as Designing Data-Intensive Applications. That's the whole story here. On r/programming the pairing is treated as the two-book canon for distributed systems, with both surfacing in the same breath as "the best resources out there". Nobody is calling it a masterpiece. Nobody is calling it bad. It's the book Reddit reaches for when DDIA is too dense and teachyourselfcs.com is the next stop.
Community feedback & reader fit
Themes
- · the DDIA companion role
- · storage engines: B-trees vs LSM
- · distributed systems fundamentals
- · easier on-ramp than Kleppmann
- · teachyourselfcs.com adjacency
Common praise
- + r/ExperiencedDevs keeps recommending it specifically to people who found DDIA too dense to finish.
- + The storage-engine chapters get name-checked when someone asks how B-trees and LSM trees actually differ in practice.
- + It shows up on r/programming as the second half of the distributed-systems reading list, right after DDIA.
- + Multiple commenters frame it as the book that makes the DDIA references finally click.
Common criticism
- − Only 7 mentions in 7 years across all four big programming subs, so most engineers haven't read it or aren't talking about it.
- − It almost never gets recommended on its own; the recommendation is always "DDIA plus this".
- − Last r/programming mention was October 2022, so the conversation lives almost entirely on r/ExperiencedDevs now.
- − No one in the sample defends a specific chapter or argues with Petrov's choices, which suggests light engagement rather than deep study.
Who it's for
Read this if you opened Designing Data-Intensive Applications, got to the replication chapter, and quietly put it down. Petrov walks the same terrain at a slower pace and with more concrete storage-engine detail, which is exactly the pitch r/ExperiencedDevs makes on its behalf. Working on a database, a queue, or a replication layer at work? It's the book to keep open on a second monitor. Already comfortable with Kleppmann and Tanenbaum? You'll find the overlap heavy and the unique-to-Petrov material thinner than you hoped.
Mentions over time
Top subreddits
Which Reddit comments matter for Database Internals?
Top-upvoted quotes across the subreddits where this book is mentioned. Click through to read the full thread.
“I haven't tried putting it in writing but I do actually save the diagram files and text files. * screenshot of the diagram: * Link to an editable copy of the diagram: Another option is to set the …
“I would recommend giving the book list at teachyourselfcs.com a look. Learning languages and frameworks can feel artificially shallow and not truly deep, so why not dive into the CS fundamentals you enjoyed in your undergrad? A great book from that list is Craftin…
“DDIA is more of a reference book than a 'learn how it works'. I would recommend reading Database Internals by Alex Petrov which is much more of an easier read than Kleppmann's book in terms of getting familiar with the problem space.
“Could probably make a separate post on this. Biggest helper: mock interviews, reading actual designs in my current company and doing them, chatgpt / claude for discussions Books etc: DDIA- by itself that book is more of a huge overview. You should look at the references and read the papers / ar…
“Yes, I've read the book, obviously, that's why I recommend it at the end as a source of more papers to dive into. If you're into distributed systems, both Designing Data-Intensive Applications and Database Internals might be the best resources out there.
“I think the books that had the biggest impact on me as an engineer would be: - Designing Data-Intensive Applications by Kleppmann: While it’s framed as being about data, it’s really the best overview of how modern high-scale systems that surround us work. Pairs well with Web Scalability for Softwar…
Convinced? Pick up Database Internals
What else does r/ExperiencedDevs read?
Other books mentioned in the same sub, ranked. Shared-sub overlap with this title breaks ties.
Designing Data-Intensive Applications
Martin Kleppmann
A backend engineer's field guide to the tradeoffs behind every database, queue, and distributed system you will ever touch.
The Pragmatic Programmer
Andy Hunt
Two veterans hand you a checklist for the craft: don't write code you don't need, own your tools, and fix the broken window before someone else does.
The Mythical Man-Month
Frederick P. Brooks Jr.
Fred Brooks spent the 1960s building IBM's OS/360 and wrote down everything that went wrong — in 1975, and it still lands.
A Philosophy of Software Design
John Ousterhout
A Stanford professor's 200-page rebuttal to Clean Code, built on interface depth rather than method length.
The Manager's Path
Camille Fournier
A software engineer picks up a management role and finds out — via 142 Reddit mentions — that nobody told them about the crying, the firings, or the 90-day onboarding clock.
Staff Engineer
Will Larson
Will Larson interviews the staff engineers Reddit wishes it had access to and explains what they actually do after they stop writing code all day.
Database Internals — frequently asked
Is Database Internals worth reading if I've already read DDIA?+
Depends on what bounced off you. Reddit's pattern is the reverse case: r/ExperiencedDevs commenters (4 of the book's 7 total mentions) recommend Petrov to people who found Kleppmann too reference-like. If you already finished DDIA and absorbed it, the overlap is heavy. If the storage-engine chapter felt thin and you want B-trees and LSM trees in more depth, the upvoted recommendation explicitly calls Petrov "much more of an easier read" for that material.
What does Reddit think of Database Internals?+
Quiet approval, no arguments. One top comment on r/programming names both as "the best resources out there" for the topic. Nobody pushes back, nobody evangelizes. It's a working recommendation, not a religious one.
Should I read Database Internals before or after DDIA?+
Reddit's answer is after, but only if DDIA didn't stick. The 13-upvote r/ExperiencedDevs comment treats DDIA as the overview and Petrov as the follow-up for "getting familiar with the problem space". If you're starting cold and want one book, the same threads still push DDIA first. Petrov is the second book you reach for when the first one left the storage internals feeling abstract.
Is Database Internals still relevant in 2026?+
Yes, with a caveat. The most recent r/ExperiencedDevs mention is December 2025, so the recommendation is still live. The book's content on B-trees, LSM storage, consensus, and replication is foundational rather than trend-chasing, which is why the ExperiencedDevs threads keep surfacing it years after release.