How to structure/coordinate multiple databases? -

imagine large corp dozens of companies, each own website , each website have own unique functional requirements

• most data on each website specific website

  • each website can edit own data

• some data shared across websites

  • there central cms allowed edit data, other websites can read , use data

e.g. you're planning infrastructure company owns multiple sub-companies make different kinds of products, in same category (cereal, food), others in different categories (books, instruments). marketing websites, crm, online stores

• there list of regulatory requirements affect products
• each company should manage status of compliance of own products each requirement
• when new requirement surfaces, details regarding requirement should entered once

how multiple databases coordinated?

edit: added more info per bob's suggestions

thanks incredibly insightful questions!

• compliance data not shared, silo'd within each site
• shared data on 1 enterprise-wide database, "types of [thing]"
• no conclusive list of instances they'll used it'd populate cms dropdowns individual sites.
• changes shared data occur few times year.
• ideally changes reflected within few minutes, hour or should acceptable
• very low volume in shared data.
• all dbs new, decision on db pending current investigation.
• sub-systems expose rest api

i agree chris that, after both sets of questions, there still big set of possible solutions. instance, if databases same technology, , shared data stored in same way in each one, db-level replication central db others. ok have 2 separate dbs per application (one shared stuff , 1 not-shared?) - influence kind of replication.

or have purely code solution, clicking publish in gui updates central db calls set of apis update other dbs. or micro-services - updating central db creates message on shared queue, picked services each after different db , apply updates in whatever form makes sense db.

it depends on (among things mentioned) organisation's technology strategy is, technology , skills have in-house, , on.

so architecture question db question.