If you're in trouble and cannot find an answer to a question which goes beyond Stack Overflow...
If you have a not-so-usual solution for your problems but need to justify it to your boss...
If you like to think on your own rather than blindly follow "common wisdom" and "profound truth"...
...then 'No Bugs' Hare on Soft.ware might be the right place for you.
Your mileage may vary. Batteries not included

System Architecture (and it’s subfield Software Architecture) is a discipline which is surprisingly poorly covered. In a sense, it is still more an art than a science, and usually requires somebody intimately familiar with practical systems, to tell what’s to do and what’s to avoid when building a system.

IT Hares have lots of experience in both Software Architecture and more general System Architecture, and are trying to share their knowledge (and more importantly, their feelings) about them.

All Not so Common Wisdoms about System Architecture, page 1:

Scaling Stateful Objects

Quote: “it is DB which is usually The Bottleneck™ – it means that we’re saving this enormous amount of load, exactly where it really matters.”
Another Quote: “as discussed above, the real-world task is always about scaling the whole system, including database; and in this regard Stateless-App-based systems exhibit significant problems.”

Gradual OLTP DB Development – from Zero to 10 Billion Transactions per Year and Beyond

Quote: “to make an efficient representation usable for OLAP – we need to modify our data on its way to OLAP replicas”
Another Quote: “Each of the DB Server Apps is a replica master, but all replica targets are within the same Replica DB”

Representing The Same Data Structure in SQL and NoSQL (from Classical Codd-style SQL to Key-Value NoSQL with SQL-with-XML and Structured NoSQL in between)

Quote: “while duplication MAY indeed improve performance – undue duplication also MAY hit performance pretty badly”
Another Quote: “NoSQL will usually call for another denormalisation on top of what we’ve described above for SQL-with-XML.”

OLTP. Compiling SQL Bindings.

Quote: “If we’re speaking about millions transactions per day over just a few hundred of different SQL statements – compiling those statements a million times (instead of a few hundred times) will be a dramatic waste of resources.”
Another Quote: “Once upon a time, I observed the largest C++ file in my career – it was a 30’000-line file(!) consisting merely of ODBC bindings (and that was just for 300 or so SQL statements)”

Historical Data in Databases. Audit Tables. Event Sourcing

Quote: “99% of reporting requests and 99.9% of analytics is purely historical”
Another Quote: “Information within the audit table should be sufficient to validate/justify current state”

Ultimate DB Heresy: Single Writing DB Connection. Part II. Gradual Scalability. All the way from no-scale to perfect-scale.

Quote: “And after this split of USERS table, the system has achieved perfectly linear scalability.”
Another Quote: “Start with a simple single-write-connection DB, with reporting running off the same DB”