SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29e0440eda5950fc9085ff326a2d1a0bdeb424ae335447048d9388b615094e2f' 
  AND token = '1RGhy6QOb96SBxTbVGnjssYPR7+XHpH3KJEu/RZL1Ho=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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