SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af09715b9ecb7388849dd3ee6b61f031751c4c1ec93a690f1352e7a93dae137b' 
  AND token = 'PbvSpAe4zxjk1EkTHt7ZuJzOZuwRw/+hTspGcpTvohY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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