SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b7fd10c76a3b679a3ce8c854d823f742eea4a661b66ee5da8f17f5b6278a21a' 
  AND token = 'X/TiB5liKX/T1CGDsjHoA70IYWhJm9kZfBLZGOdFStY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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