SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c50d27d78ca16106a2270e63f6ab03e79ecd7f165534fb2e48d68365d39e979' 
  AND token = '/0hBiFTmuRN8GtxztvXDQOyiRxVzBJs8DY0WWn/Aowg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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