SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6767f40cceca47923853b85723896a59e2f43e957553895e6f1313fd63fefc0f' 
  AND token = '4pF+uVEu1Eu3PyqLWMSD54bhQwRJH8psbxZrKum8NkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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