SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fcc2a7794d8ff00866a252a33f706def4ddb2ee154de2ecfba86895ef435f4a8' 
  AND token = 'hkvuJOPXGKuz27e9BMFit//WBktxIphWtMcjbqA6Dz8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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