SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '646caeb3fee15e77a1e7b51314c9bed2492b5b0969c46193fe3f90c092c07c6c' 
  AND token = '4p6j0vB5CDy46ZRPbp+7EUVc8zKY+jj0tt3uXtaaYF4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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