SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '515e43f0d0a94b14cd7ee7e57771bd30d715f601ed3cdfa75f63a66a81193735' 
  AND token = 'q52R5edkxcDb1OqB+qucJE7+JpGErv0tVjW8NgmDwY4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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