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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5b9defc31e2db709e471545506f905fb9b39533035f3db9914c5add0651ece3d' 
  AND token = 'Kg+IoVGG/lCWlK+392LwUx64P5BKvlVynvEoGQJH504=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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