SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '021b3950c380a022825cd80a45c70d316e0a0befc50cf81daac084612e040503' 
  AND token = 'wLiwq6bMTyK6HZoXyCq613fZPClS6JsW6xUKjbYoGzQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}