SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73977c7f5c6fb279c8066d63fc8ad0e5a07d826bef5c04df734f70a9760dd831' 
  AND token = 'uO/hqjeZIsCSvCAYcZW7FlvGSDqeUlCoW5RUJKUXgpE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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