SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4c068dc6d108d6f54ffa48a147d01654efe08592a7aadadb86486c000bac602' 
  AND token = 'uEnVHGROYgBVJvUThd35WmTGXERYt+gctrB/j+L1CQE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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