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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3dc022db1ec92a4a3929bcf4a9fb96c6341fc67f19e0d92615221297558b684d' 
  AND token = 'ZxNy7FV3IkSvkdEwb3MzNnvZOE9defHtln9UzLqytvE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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