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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6e71378f7ce90961c1efdba02db1627d0af06e2df679b5183e20aa6eaa67b4cd' 
  AND token = 'P8sNzT+xOplC8nPLi1CCLv8JTJ/F5D97EKxH5fTe+/I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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