SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '535bea194dd01371ae5822a6b555c490bda9853ad7c47685afb4a85d84851988' 
  AND token = 'DhAGtFUBEuZd50g1rIuVV9vMa135vwOob3eujA+GtG8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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