SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '791d502c688187368202eaf89f1a398105f2045bd242f62dd427ce62febc1003' 
  AND token = 'yHbwN3VlQ6B7Qpna4Tz+rGD8Mpi3U8cvhlFpRvqhWX4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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