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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '53e4aa826cc1d6761181892589f6d73f9168c5009c16a1859c801a77352cfc19' 
  AND token = 'MBEhKBt0PSuMKlTOrlRtXGOIwxn3U9a9+GhyDl506Og=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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