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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'bc658d4782ca95f98d07858c80afc2c55480e0fa3b692fafafaabe70a35ad8b8' 
  AND token = '9ymTB97Pirql9Nyc5SFwRHy9lh3WICu19dVLumVfkwE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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