I’ve setup many views based on a single large table. How much of a performance penalty will I pay?

A view is syntactic sugar for a canned query. Unless the view is referenced, it does not expend computational resources.

See also: view, views, :: , .z.b and \b

How can I set a trigger on a kdb table?

Triggers went away in k4; kdb does not provide a table trigger mechanism. However, your needs may be satisfied with views and/or the function .z.vs

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