SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78574a3dce34f4b5329c48d8e500d1e72c9febc6e65589582d9975bc03fb08d0' 
  AND token = 'xOp5hIDBwnKRIZL3PNDAFz+tAt6BqMUbdft2KS9Fzpg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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