When to use Redis instead of MySQL for PHP applications?

Question

I\'ve been looking at Redis. It looks very interesting. But from a practical perspective, in what cases would it be better to use Redis over MySQL?

Answer 1

Redis, SQL (+NoSQL) have their benefits+drawbacks and often live side by side:

• Redis - Local variables moved to a separate application
  • Easy to move from local variables/prototype
  • Persistant storrage
  • Multiple users/applications all see the same data
  • Scalability
  • Failover
  • (-) Hard to do more advanced queries/questions on the data
• NoSQL
  • Dump raw data into the "database"
  • All/most of Redis features
  • (-) Harder to do advanced queries, compared to SQL
• SQL
  • Advanced queries between data
  • All/most of Redis features
  • (-) Need to place data into "schema" (think sheet/Excel)
  • (-) Bit harder to get simple values in/out than Redis/NoSQL

(different SQL/NoSQL solutions can vary. You should read up on CAP theorem and ACID on why one system can't simultaneously give you all)