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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '574f2a230533c56f94a397c80053559afa9af3b999afce5a65fd9be0b8fecfa9' 
  AND token = 'iTn0YJ/in9KcstHG6KMqe6KTKj9KL28XbFFl8DF8CR0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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