SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d8277270de7486d864d89f6fee84a581c016ad478b7f616cffda7de628091af' 
  AND token = 'GLsTkfQHUYC69hf03CRMuwJpwjky/+ThpC3bwQ+pp9g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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