When to use LDAP over a database?

Question

When should I use LDAP vs. database/key-value-store/column-oriented-database/etc?

Answer 1

also nice to read:

There is no simple answer but the following notes may be useful:

1. The performance hit during writes lies in updating the indexes. The more indexes (for faster reading) the less frequently you want to update the directory. Read:write ratios of less than 1,000:1 or higher for heavily read optimised LDAP directories.

2. LDAP Replication generates multiple transactions for every update so you want the lowest practical update load (1,000:1 or higher).

3. If data volumes are large (say > 10,000 ) the time to update even a small number of indexes may be serious so you want to keep updates as low as practical (10,000:1).

4. If data volumes are relatively small (say < 1,000 records), indexes modest and no replication is being used we see no inherent reason why you could not use LDAP in a form which approaches a transaction based system i.e. every 5 - 10 accesses involve a read followed by write cycle (a modify in the LDAP jargon).

5. We suspect that the real answer to this question is (with apologies to the memory of the late, lamented Douglas Noel Adams): the ratio of reads to writes is 42!