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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8c9c70f6fd09a9a08f10eaf4720999f8c2923d3e4e5ed2f06288dd288ca0fba' 
  AND token = '6HfQ3eaJ1NsexdGgWGFRoTRdUEtuJKmPbyrgfKh83mM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}