SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db577556315141514be3ecc8ded19702ff58235419910b86fc721edc799691b5' 
  AND token = 'w9gYxnUWzbAz6L2NUM/uQ+9qcjU+JRTCCUJx9E3LlvY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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