SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50b21926daa37eb0f02f8446c2113af86c904568370f9ff52afc93a638d75e27' 
  AND token = 'g+LZlrkobrVdQku6Ulq4qVj/SK5xjp7ZDCKE3U3k4yM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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