SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56acd2f1d958fd8eed00d5eb968ad34ac81603b222f26f208176cb497539c192' 
  AND token = '31Yes8CBcP00HE0/gw8GQ4zgoCppqcF2aDn2vYpNcUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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