SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3708ea29819624c2df48be1e0b93c616c46a51ad36c29c7e6c195846da826206' 
  AND token = 'HBKGXpBWZOLwTBItwDpoXl64zHDla4GUQRoDoZT9n90=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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