SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '535702a2343070caad01307fa294a6222a2e263ccaadf4466ad8ddf625df34ce' 
  AND token = 'GiSmWcl5TmZxSnIBvHbDaGJ5YVZI2WEgAg48mw/ZacE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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