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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5b41b93c05898df401a98d83a6d99d7b10a88d34008d12d8ed2cabe6af96214' 
  AND token = 'WqjpuRy9AzLyJn+uAmMVTtHPkMsotEDFeX0gyjwvShQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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