SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51216831505ba892c6b56554a1435ad329d1c9eb10a3a5ad71a1e09b6580f08d' 
  AND token = '/UjtVkm4IIfuKaCX3wMPfd73VCK2sdYYfLPh/KcHw4M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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