In addition to Postgres, Heroku offers a hosted Redis solution.

Heroku has a detail post outlining the hardware they use to run Redis.

Comparison

Many Heroku Redis tiers run on multi-tenant systems. For these tiers, it’s difficult to estimate the underlying instance type, so I’ve left them blank.

I don’t know how many replicas Heroku uses for their dedicated instances, so costs may be off drastically depending on the amount.

It was challenging to find corresponding instance sizes for the memory provided by each tier. Many of the instances I found have significantly more RAM than specified by Heroku (e.g. 244 GB for cache.r3.8xlarge).

Plan vCPU RAM Multi-tenant Instance Heroku AWS (1 replica) AWS (1 replica, reserved)
0 2 50 MB yes — $15.00 — —
1 2 100 MB yes — $30.00 — —
2 2 250 MB yes — $60.00 — —
3 2 500 MB yes — $120.00 — —
4 2 750 MB yes — — — —
5 2 1 GB yes — $200.00 — —
7 2 7 GB no cache.m3.large $750.00 $95.76 $58.60
9 4 10 GB no cache.m3.xlarge $1,450.00 $191.52 $117.37
10 8 25 GB no cache.m3.2xlarge $3,500.00 $383.04 $233.42
12 16 50 GB no cache.m4.4xlarge $6,500.00 $576.00 $333.04
14 32 100 GB no cache.r3.8xlarge $12,500.00 $1,915.20 $1,016.22

Like Postgres, the private tier redis is the same as the premium tier, but with a higher markup.