SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3e0258162814df60a7b123d4a47abf1ec23097fbf013b7e9945726df684b900' 
  AND token = 'fYzkcVjUoieg8AcIpVLe5GOQOeplqIENvhfOMD2V+tE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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