SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9256ceb58100ee28c1fa451ce4ea66ed83accbce167534f4f7b2b9a687251484' 
  AND token = 'koAU1JcSTinV0CnXTp1I4DPbtDfq/5pu5kP6EBjHmOQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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