SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '63571029aa9fcd1a2a7c8504dff499a7972f33a86f21560d44bd70c3b3b630d4' 
  AND token = 'jg6YVeVKFSLK91hVdjDB7xxOha6sUGBltrAQpWofuBI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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