SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c294e198462f55035484346c75a5c35f03ab70fc2c2bf102a2f0e85e5aa95407' 
  AND token = 'PBXoVqPoJcZFk4s5YFkIezQWSOBmHEvXaWLaNvz9PzA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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