SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c8edde179bf11672c0267c0af6f02f42293786a294c13636dc5236009a63be1' 
  AND token = 'PZCTkiKF1dpidNqqb25kUo2tYAlc4zI3lbaAUqsMlAo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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