SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e4a38fe4438eb661db979954155e1a215ff65835b22121ffd718f43cd295702' 
  AND token = 'OOQq18QeO+pMUw5861NipmCoGv+nXUDgp9vx96WiTn8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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