SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f21280705f09297059da4480338097879a2cbd903611255266059dcce3f0b09c' 
  AND token = 'LxttsRaT1Jj01qBdznbgmpreTpd53d23KQ0oCZDtpKo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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