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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '42aee48bfb3fe13c1068765e95993daf6d317bfb4b022cf842f2af9ab8b71c56' 
  AND token = 'NE4i8Nx7RdDnC8ZXEzMtaxbDoXdKuKdhNjAsLvWCHYI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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