SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3690557b4208970b46099a44c8324f8870ebb5feb2febc8faefa2c61b839a83' 
  AND token = 'UVOaJxNYpNlI3UWj5wBeeNDHj5K0eH+WSCvLqqNlcEE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00094

JSON explain

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