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From that post mortem: It was unfathomable to us why people would choose a system that barely does the thing it’s supposed to do (store data), has a big kernel

From that post mortem: It was unfathomable to us why people would choose a system that barely does the thing it’s supposed to do (store data), has a big kernel lock, throws away errors at random, implements single node features that stop working when you shard, has a barely working sharding system despite it being one of the core features of the product, provides essentially no correctness guarantees, and exposes a hodge-podge of interfaces that have no discernible consistency or unity of vision. I mean... that's unfathomable to me too. He explains it later, that " MongoDB turned regular developers into heroes when people needed it" I have a hard time understanding why devs choose / chose MongoDB. Postgres with JSON columns gets you so far, why would you go with MongoDB, given the issues it's had?

s_kilk 9y ago
> I have a hard time understanding why devs choose / chose MongoDB. Postgres with JSON columns gets you so far, why would you go with MongoDB, given the issues it's had? Jsonb is a pretty recent addition to postgres, when compared with the MongoDB timeline. And even today postgres still doesn't have the replication/failover story that made MongoDB pretty compelling. I know, it's coming, whatever, but the point is that there was a time where if you wanted a json store that could stay alive through network issues, MongoDB was one of the only choices available, and postgres simply didn't have what was needed.
- tensor 9y ago
  The problem with that thinking is that the replication mattered. I'd argue it didn't, it was essentially a scam that people fell for. Who cares about failover when you're losing data due to a bad implementation? Who cares about replication when you can gain the same performance by using a performant database on a single node? Did mongodb truly allow anyone to really horizontally scale? Most places that need massive horizontal scaling using something like mysql as far as I know.
  - imtringued 9y ago
    The thing I don't understand about mongodb is that it makes a tradeoff for scalability. The secret ingredient in the horizontal scaling sauce is giving up inter node ACID transactions. Nothing prevents you from making the same tradeoff with mysql or postgresql.
    - eloff 9y ago
      Indeed, that's how youtube, twitter, and facebook use MySQL, among others.

s_kilk 9y ago

> I have a hard time understanding why devs choose / chose MongoDB. Postgres with JSON columns gets you so far, why would you go with MongoDB, given the issues it's had? Jsonb is a pretty recent addition to postgres, when compared with the MongoDB timeline. And even today postgres still doesn't have the replication/failover story that made MongoDB pretty compelling. I know, it's coming, whatever, but the point is that there was a time where if you wanted a json store that could stay alive through network issues, MongoDB was one of the only choices available, and postgres simply didn't have what was needed.

tensor 9y ago
The problem with that thinking is that the replication mattered. I'd argue it didn't, it was essentially a scam that people fell for. Who cares about failover when you're losing data due to a bad implementation? Who cares about replication when you can gain the same performance by using a performant database on a single node? Did mongodb truly allow anyone to really horizontally scale? Most places that need massive horizontal scaling using something like mysql as far as I know.
- imtringued 9y ago
  The thing I don't understand about mongodb is that it makes a tradeoff for scalability. The secret ingredient in the horizontal scaling sauce is giving up inter node ACID transactions. Nothing prevents you from making the same tradeoff with mysql or postgresql.
  - eloff 9y ago
    Indeed, that's how youtube, twitter, and facebook use MySQL, among others.