SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '82b9599047916f1c71d98c166385a65835b776d1e924288e5f8e070d2d065676' 
  AND token = 'q/HrmXgGx2VrRdV8T4AbQoDzm6HecK7VzGf/JB6wPfc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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