Rails performance optimisation tips

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Classic Rails performance optimisation tips Alessandro Lepore

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“Please make the site faster” - Any client

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“Ruby is slow” - Anyone

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“This is actually fun!” - Alessandro

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Backend

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Measure!

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Measure!

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DB is fast, Ruby is slow ● SQL is awesome ● SQL is complex ● pluck instead of map ● order instead of sort_by ● any? instead of present? ● size instead of count or length ● find_each instead of all ● select to limit fields ● Avoid collection.to_a ● N+1 queries are not always bad

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N+1 queries are not always bad

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Useless data is always bad

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Tips ● Measure ● Avoid mistakes ● Cache all the things! ● Use recent Ruby versions ● Try optimised gems (fast_blank, fast_jsonapi, concurrent-ruby-ext etc.) ● Know your language (GC, Heap, Constant cache etc.) ● Concurrency / background jobs ● Ruby fine tuning (ENV vars tweaking, alternative malloc) ● Also DevOp

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Frontend

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Measure! ● PageSpeed ● YSlow ● Speedcurve ● Chrome DevTools ● Lots of other tools

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Tips ● Limit response size, optimise images ● Defer Javascripts ● All those things that Rails is already doing ○ Single file, minify, compress, hash etc. ● HTTP headers ● Limit connections ● Split critical CSS ● Limit or async web fonts ● Use a CDN ● Try new technologies: HTTP/2, WebP...

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