SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fa878da14a26de944ee3ab2d6d5c20b30eefe7780888473ed356b39e9180afc7' 
  AND token = 'gPlDZINI44KCTSNfmdnn88MnP42tvD+t8JMgLMBENv8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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