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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5ce2b49178f69a9d9d87e20c253709dcc8c53c9e9f4b9fccca015499a29b0688' 
  AND token = 'I2g49F7XP7DwLJsCsk4hjdIDVU7PNYwiKHmhLdkLEqo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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