SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e729ee0056f8fbc2b52d944e5a2f127737aa1153b5349c9950e70b03d638da40' 
  AND token = '46W+m30rWYZVnMdkFJdB95hv4LGYlGquGxwb740qK3M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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