@@ -84,3 +84,42 @@ The following describes at a high level the series of steps for processing
84841. Load up most recent build plan
85852. Convert build plan into constraints for next build
86863. Continue from step (3) above
87+
88+Frequently Asked Questions
89+--------------------------
90+
91+__Why does Stackage have an older version of a package than Hackage?__
92+
93+There are a number of answers to this question:
94+
95+* Simplest reason: how old of a Stackage snapshot are you using? Once a
96+ snapshot is created, it's frozen for all time. So if you use
97+ nightly-2016-01-01, by the time you get to 2018, it will be pretty dated.
98+* If you're using an LTS snapshot: we lock down major versions when
99+ first creating an LTS run, so subsequent minor versions will not get
100+ new versions necessary. For example, if LTS 6.0 has `foo` version
101+ 1.2.3, and the author immediately thereafter releases a version
102+ 1.3.0 and never releases another 1.2.\* version, you'll never get
103+ another update in the LTS 6 line
104+* Sometimes we have upper bounds in place because other packages have
105+ problems with newer versions of dependencies. Open up the
106+ [build-constraints file](https://github.com/fpco/stackage/blob/master/build-constraints.yaml)
107+ and search for "Stackage upper bounds"
108+* Wired-in packages - those that ship with GHC and cannot be upgraded,
109+ and packages depending on them - are fixed to GHC versions. Common
110+ examples of this are containers and transformers. There's a lot more
111+ information on this in
112+ [an FP Complete blog post](https://www.fpcomplete.com/blog/2014/05/lenient-lower-bounds)
113+
114+__How long do you maintain an LTS build?__
115+
116+We only guarantee that we will maintain a single LTS major version at
117+a time, and that it will be maintained for at least three months. This
118+is the
119+[originally proposed support window](https://www.fpcomplete.com/blog/2014/12/backporting-bug-fixes),
120+and hasn't changed since then.
121+
122+That said, we do maintain the capability to keep multiple LTS runs
123+operational in parallel, and with LTS 6 and 7 in fact did so. We
124+aren't changing our guarantees yet on longevity of a release, but are
125+trying to push out the bounds a bit farther.