SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b21eb904a2cc625e0a8f126c64d3d28e3d68b658b9ff583174321b0fc49f415d' 
  AND token = 'zr20dVv5uJLc+J1PK1mCirLOZ0F+49ZGq+n3Wfzy2j8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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