SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51afc76633b61f948433f424f8fe8ab2d828f2744aa2c4b9312bc79944f5aef0' 
  AND token = 'FSIuo8upGkekTvNCbL5YsrKgBnt3AL45DiUNwFCGE04=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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