# LMDB Hacker Approved page: https://hackerapproved.com/p/lmdb/ 17 people recommended LMDB in Hacker News comments, 5 had mixed feelings and 12 criticized it, November 2025 to October 2026. It was recommended in 9 of 12 months, in 12 threads. It does not meet the Hacker Approved badge rule. 9 of the 17 people who recommend it commented in one thread, “Lightning Memory-Mapped Database Manager (LMDB) 1.0”. **Verdict:** Fast, memory-mapped embedded database that people trust for reads and large datasets, and crash-safe with default settings. Critics say writes slow down as databases grow. Summary written by Claude from 36 comments. It was written before the November 2026 recount, and 35 of those comments still count. ## Why people recommend it - Fast reads, memory-efficient (4 comments in the sample): "Because it's so efficient, it can retain more useful data in-memory than other DBs for a given RAM size." ([source](https://news.ycombinator.com/item?id=46113507)) "if the object mapping fits in memory that should be pretty optimal for reading" ([source](https://news.ycombinator.com/item?id=46137646)) "getting a 22x speedup by replacing SQLite's btree code with LMDB" ([source](https://news.ycombinator.com/item?id=46524193)) - Crash-safe by default (3 comments in the sample): "By default, LMDB performs whatever necessary syncs and is 100% crash proof, even in the face of power outages." ([source](https://news.ycombinator.com/item?id=49023294)) "As long as you stick to the safe LMDB options, which are the default options, it's reliable." ([source](https://news.ycombinator.com/item?id=48767630)) "LMDB is already used by OpenLDAP [2][3] and seems pretty bullet-proof." ([source](https://news.ycombinator.com/item?id=47009233)) - Reliable in production (3 comments in the sample): "I've used LMDB in production for multi-terabyte databases, and we encountered the long-write time but found a solution." ([source](https://news.ycombinator.com/item?id=48768862)) "LMDB, boltdb/bbolt and sqlite (with mmap) are all rock solid." ([source](https://news.ycombinator.com/item?id=46511045)) "It's truly an incredible piece of tech." ([source](https://news.ycombinator.com/item?id=46553159)) - Handles databases larger than RAM (1 comment in the sample): "LMDB fully supports multiprocess concurrency as well as DBs multiple orders of magnitude larger than RAM" ([source](https://news.ycombinator.com/item?id=46070399)) ## What people warn about - Slow writes on large databases (3 comments in the sample): "once the db reached several hundred gb, writes would hang for longer and longer periods of time" ([source](https://news.ycombinator.com/item?id=48767614)) "It is really reliable except write performance in my experience." ([source](https://news.ycombinator.com/item?id=48767586)) "lightning fast on reads but quite bad on writes" ([source](https://news.ycombinator.com/item?id=46734233)) - Unrecoverable after a crash (2 comments in the sample): "but then the whole database can be unrecoverable in case of crash. It has happened to me." ([source](https://news.ycombinator.com/item?id=48773497)) "a default database that isn't robust against power failure or crashes seems suprising to me" ([source](https://news.ycombinator.com/item?id=46327927)) - Hard to use from documentation (2 comments in the sample): "I find this almost totally unusable. I often find myself reading the source instead." ([source](https://news.ycombinator.com/item?id=45925501)) "From this documentation I don't know how to use lmdb to make a correct program." ([source](https://news.ycombinator.com/item?id=45952057)) - Unusable for many use cases (2 comments in the sample): "I think lmdb is mostly unusable, for many use cases." ([source](https://news.ycombinator.com/item?id=48769429)) "Don't use LMDB for anything that matters." ([source](https://news.ycombinator.com/item?id=48768212)) ## Other key-value stores people recommend - [RocksDB](https://hackerapproved.com/p/rocksdb/): 17 recommend, 3 mixed, 3 criticize - [Cloudflare KV](https://hackerapproved.com/p/cloudflare-kv/): 8 recommend, 0 mixed, 12 criticize ## The badge A product earns the Hacker Approved badge when at least 10 people recommend it, recommenders outnumber critics at least 2 to 1 (mixed feelings count toward neither side), it was recommended in at least 4 of the 12 months and in at least 5 different threads, and no single thread supplies more than half of the people who recommend it. Health and money products are never badged. ## Cite as Hacker Approved, "LMDB", https://hackerapproved.com/p/lmdb/ (17 recommend, 5 mixed, 12 criticize; Hacker News comments, November 2025 to October 2026). Counts updated 2 Nov 2026, with data through October 31, 2026.