SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12f50bf7dfb2015f725b2ff416c1381da3e6cbe8a0ce548ea2673ff2d5b081a2' 
  AND token = 'HqDQWMUYiSBC2iUfMH+j51w5LhXdYxz0VosJjcK2/DI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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