SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0394005d867ce6fba34183f29ea8a784c4a142196cd98fa19216f30193386172' 
  AND token = '7ZoyayBXaEERU12sbSVdNr3NC9mH9jhrqlf1ZXMnKT4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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