SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '31600e58ef90910ed96bba1fbefdbef88ced715ba2b6f5f33fbff5b818482c22' 
  AND token = 'zRLvLPczrafj9PLWdyVM+miEkWZVjwTwNqOHiLkyCu0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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