SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12e1c8086ded926828fd1e4c79adf2a6b84f7bb9110d0ad22c1cbbc58a00740e' 
  AND token = '/TCKhBQgGM4MVC+AppeivGuUB5xoileCAJdgyGgjBaw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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