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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7a12d3b117a365bb8e4ba6ec1b35d68738498952ae27a4dd378139d4b2e85908' 
  AND token = '3VvV3VgrVFrhV4M8j7WpQV2zMKaaFfbVgGwwBW2Mj8k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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