SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dfc855a468381dad08adc460112c80f9653c329292a7b6634511781ef6e15134' 
  AND token = 'MkOvILALIseDn/xqMq7jR0z6RNBrxvqvZiBJAjZzQ4o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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