AWS ElasticSearch is now offered as part of free-tier, under which they are even offering "t2.small.elasticsearch instance" which is even not available in free-tier EC2 instance.
You can create both t2.small instances and install your own ElasticSearch in the free tier account for which you normally have to pay around $20 a month, Also you can create an AWS ElasticSearch service using "t2.small.elasticsearch instance" which would be totally free.
Also "t2.small.elasticsearch" can easily satisfy your testing and small size index and moderate traffic.
Providing some tip to avoid cost:
1. You can write a lambda function which would automatically stop and start instances, use that to start instances only during traffic hour.
2. Use spot instances to avoid the costly reserved instances and choose the regions which offer cheap pricing
Hope this Helps!!
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