SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3eb824075a747716b088e43d7037bb3f28984a6beaca1201009418c66ec9345' 
  AND token = 'D4BKTlDnNyLBtmEBR7Zxj4a7tfNoYZYQNXQjYxCIyVY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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