SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '16b74e8c8e2986c9c078932308e208824932b07b81deb35eb886b723b8c6a711' 
  AND token = 'gRj7eWoW1ELEMcQBrF0RHdI8aZxCPJG49+6EEhL6wWo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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