SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '389b8065ea6088fa42f13919919667e39e48a1bea10741e07a00a3c3fce29b0a' 
  AND token = '3mSto7aneE0WdRZjKkHaJFB1VIYrq8xXIIKHvNlULVo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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