SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fc2bf15b6bec662a685a167babc4d8821f1c37d6fb3bd1544058de76a0f062e' 
  AND token = 'TRAnjCWTbBPk1rEI9XBnnMteWpEF84u+rE0quWsGV3w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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