SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51955ff95cda1c59c5f8ea239f604e005d7249a8bd188dfc2c939270d2c0ec25' 
  AND token = 'OVtKG4NZpvJeYJvCy73MKz0gmjtdFdb3LhG3/FYUZ0s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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