SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31250004d355f6debe166254b7d31af2ad82d00b5ed66510d4eb1be46644ce83' 
  AND token = 'P/26g+wlh1DL4FHVTKsRrvFfn6rhSun60ywLsEs2FQI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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