SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ee7730a70e3368ec5d715ecdfe1929440a26284688cb9bb399553242f721b68' 
  AND token = '7qZgfOs+z2imOKjQbbXniIVlLEPIhX/du8AgbPdhQeA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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