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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4d3cefb8d8f9675d5987ad4ec2ff8f25ccfb0e5387509a1fb5ff8c5079788788' 
  AND token = 'eaK+OBRNMgaEISCb0VXWS0WRfn5DxRFLM3DjN1ItV9k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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