SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe800a3d0dbd500008ed2bbdd61276d43efe5ef10a9039f2fe5efbe5da05eb05' 
  AND token = 'MD9HY2HzVuGw8WGxjzQRaM8c6AiATKhlu1tVsjLUeUU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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