Check more deeply. If you then identify a problem with too rapid penetration of dryness then cover the soil with a mulching material - coarser in texture than the compost - that will keep the sun from baking it.

Also: if by your description you are saying pretty much no rock particles (sand, silt, clay, in order of decreasing particle size) were included in your mix then in addition to poor moisture retention you may encounter soil mineral deficiency issues also.

"... raised bed soil, coco coir, work castings and compost ..."

There is a missing ingredient here: dirt. These are all fine amendments, but the primary ingredient for organic gardening is still dirt, or to use Embothrium's term "rock particles". You are trying to garden in a compost pile, rather than in soil. What kind of soil is underneath all of this? Is it sandy? Clay? Whatever it is, your garden will be better off if you dig down and turn all these amendments into the underlying soil. The mineral plus the organic amendments will do a better job holding moisture and nutrients for plants.

Once you have soil that is a mixture of mineral and organic material, you prevent drying out by using a mulch on the top. I tend to mulch heavily - 4 to 6 inches. It actually does double duty - it regulates the temperature and moisture in the soil, and it gradually decomposes to create a layer of compost on the surface by next spring. Once you do that, you no longer have to water as often because the sun never hits the soil. Bonus: it keeps weeds at bay and weeding to a minimum.

Thank you Embothrium and Richard. I added dolomite, rock dust and general purpose fertilizer as well to the raised bed. The ground below the raised bed already had garden soil and below that native clay soil. I planted on the garden soil last year and the plants did well. I amended the garden soil with Kellogg amend before putting the raised bed on it. I’m not sure what you mean by dirt. The raised bed mix I used has aged redwood, rice hulls, aged fir bark, chicken manure, bone meal, feather meal, gypsum, alfalfa meal, bat guano and kelp meal. Sorry if I sound stupid. Does this qualify as dirt? I’m still new to soil. I started off container gardening with pre made potting soil. I had bad experience with peat moss based potting mix repelling water. Then started using coconut coir. Raised bed and garden soil is still very new to me.

What mulch do you all suggest?

Anything organic that consists of larger pieces than are already present.

Here's some background on the use of organic material for improving plant growing areas, Including vegetable beds:

https://s3.wp.wsu.edu/uploads/sites/403/2015/03/soil-amendments-3.pdf