Datomic
Hacker ApprovedRanked 13 of 22 databases by recommenders
Recommended for immutable history, time travel and Datalog queries that people find simple to work with. Main caveat: it is complex and exotic.
Recommended for immutable history, time travel and Datalog queries that people find simple to work with. Main caveat: it is complex and exotic.
27 people gave an opinion
- recommend it
- 20
- criticize it
- 7
- approval share
- 74%
Recommended in 8 of 13 months
- November 2025: not recommended
- December 2025: not recommended
- January 2026: recommended
- February 2026: recommended
- March 2026: recommended
- April 2026: recommended
- May 2026: recommended
- June 2026: recommended
- July 2026: recommended
- August 2026: recommended
- September 2026: not recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it carries the badge
- 20 people recommend itNeeds 10 or more, met.
- 2.9 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 8 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Datalog query model
“Datomic-flavored Datalog in a Clojure triplestore feels almost made to order for LLMs”
Comment from 26 Jul 2026 in “The new rules of context engineering for Claude 5 generation models” “the datalog model it implements is honestly a pretty good way to think about things”
Comment from 10 Feb 2026 in “What Functional Programmers Get Wrong About Systems” “Datomic uses datalog for its query language, and it’s excellent.”
Comment from 17 May 2026 in “Prolog Coding Horror” - Comment from 10 Feb 2026 in “What Functional Programmers Get Wrong About Systems”
Strong fit with Clojure
“Not acknowledging that Datomic and Clojure has something to do with this succes would be simply a dishonest gesture.”
Comment from 29 Jul 2026 in “Steel Bank Common Lisp version 2.6.7” “Datomic and Clojure have nailed databases and programming in a general sense.”
Comment from 29 Jun 2026 in “Microsoft's new DocumentDB rethinks NoSQL on PostgreSQL” “Both are alive and well. It's never been better to be a clojure+datomic dev.”
Comment from 11 Jul 2026 in “Microsoft's new DocumentDB rethinks NoSQL on PostgreSQL” Simple and convenient to work with
“From the DX perspective is incredibly simple to work on”
Comment from 21 Jan 2026 in “The challenges of soft delete” “It works great and it's super convenient.”
Comment from 20 Apr 2026 in “What if database branching was easy?” Keeps all past database views
“where you never remove data and all previous views of the database remain accessible”
Comment from 10 Feb 2026 in “What Functional Programmers Get Wrong About Systems” “you get time travel which is an amazing feature on top”
Comment from 21 Jan 2026 in “The challenges of soft delete”
What people warn about
Each mark is one comment
No real branching support
“If each "branch" is read only, it's not a branch at all.”
Comment from 20 Apr 2026 in “What if database branching was easy?” “neither Datomic nor XTDB support branching”
Comment from 20 Apr 2026 in “What if database branching was easy?”
Other databases people recommend
The four most recommended other databases, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| PostgreSQL | 816 | 233 | 78% | 13 | 10 yrs42 owners | Approved |
| MySQL | 124 | 107 | 54% | 12 | — | — |
| Microsoft SQL Server | 73 | 59 | 55% | 12 | 20 yrs6 owners | — |
| Microsoft Access | 62 | 39 | 61% | 12 | — | — |
| DatomicThis page | 20 | 7 | 74% | 8 | — | Approved |
What people said
30 of the 35 comments that mention it, newest first. Each links to the original comment.
“Ten years ago I was at a startup where we used Datomic, and it was okay”
“it was okay, but six months in the sales team was like “ok how do I run SQL queries so I can triage leads””
“Datomic was the single strategic multiplier that enabled Nubank's success”
“it needed the source code to the open source version of datomic”
“Not acknowledging that Datomic and Clojure has something to do with this succes would be simply a dishonest gesture.”
“Datomic-flavored Datalog in a Clojure triplestore feels almost made to order for LLMs”
“Both are alive and well. It's never been better to be a clojure+datomic dev.”
“Datomic and Clojure have nailed databases and programming in a general sense.”
“Datomic uses datalog for its query language, and it’s excellent.”
“useful for testing -- but not much else, since it is purely in-memory”
“If each "branch" is read only, it's not a branch at all.”
“It works great and it's super convenient.”
“neither Datomic nor XTDB support branching”
“It was a gamble, but it paid off in the end.”
“Clojure and Datomic are almost never supported out of the box by any tools”
“I had not idea NuBank discovered Datomic first and that it's Datomic that led them to Clojure”
“Datomic and datalog are actually completely principled”
“the datalog model it implements is honestly a pretty good way to think about things”
“where you never remove data and all previous views of the database remain accessible”
“easy to test new schemas with in-memory Datomic”
“I suggest you study Datomic and the EAVT data model.”
“it does fit Datomic really well”
“From the DX perspective is incredibly simple to work on”
“it doesn't support non-immutable use cases AFAIK”
“you get time travel which is an amazing feature on top”
“Two candidates are sticking out.”
“Datomic is very good, but extremely complex and exotic”
“xtdb and datomic can't keep up with their SPARQL graph traversal”
“so I'm guessing they just didn't care about the feature”
“They intend for you to hire them as consultants and pay licenses.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.