SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ae9ee6c71782619ec07228785173af7829350d494579afbcf5868a0787758b4a' 
  AND token = 'XIdqnTdiJgBX3w1LWqC8oEHV0rnqCpABiUeTwgFxtJM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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