I would also use { S3 One Zone IA } which is about 20% cheaper than Standard S3. The only difference is, with Standard S3 you are getting Multi-AZ for DR,  but S3 One Zone IA you are getting one single AZ. For an AZ to go down in such HA cloud environment is very slim. Not to mention the fact that you are running a Social Network site, Chat messages & Pictures are not as critical as Financial Data. In fact, you can even migrate old objects that are over a year old or so to AWS Glacier S3 type which saves you even more money.. Keep in mind, Glacier is not used for daily storage, it is mainly used to Archive history data. Retrieving objects from Glacier can take hours. Thus, this is not something you want to use for frequent daily access.