SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76b9ed8462726d1c7a50ab54f47b2728f44399e6e93702ecfb1338e9f949da04' 
  AND token = 'PP5yZ8UH5ZCD4gZxL7crHDwq+xD/sLWyuLIFK+Apq1Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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