SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff33ab71eb7851a54632509b2cb3d4d7231823a80fb529e5679d6979f0e344d1' 
  AND token = 'sMBcUTXBkzkODoWs3iltmgrpILWAfZQ4RCdZv4h0cQw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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