SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '782c86acae91cad51b6193527196fe8e7f479aa7061ebf932f565e4837e56551' 
  AND token = 'tzBV8mOiDcbzG4v9x73rTxd5tAkEB20BLqmIk04Tmyk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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