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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6b9975c0a44905def0fa17da57f58d928ee13f989c4fa5ecd24f725d791fd020' 
  AND token = '8je2UVghRv10WXRwOMWn5QVLX1bcfTb+JnRXR1RAOUk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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