SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bf51aa69c0b7a9cdb0d54b927556c99a687512637cc46c794b24ad39eba19c78' 
  AND token = '1rDh2EDw6lfTv0xch4PD3szjLhrqFeuWuf0ZUN8qXn4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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