SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3894419d42726bd6b90906271aa717cdeed7c04a6ee09b6415be27cb8e5ddd52' 
  AND token = 'KTD/xcBZvdHZbJhjI+8flYaOlJSm+AZQ4uGumlNPWig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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