SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c389b805350872f142910650122c01983b6bc06b49a9f34736825acae7202751' 
  AND token = 'YmXbPbh2ISKT0LwQ/F3Msy53DoSroFA/KYs6bAy6nEo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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