SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56f8407742f9fce1ffa60e520585d2103bdb0c48a5f8988f32c70c8d421d82aa' 
  AND token = 'YeWhfQiRADZwrwIyTOsHdfVBFSTvBtVilbXxpmqgT0I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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