SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9f3cf0e03396ee7f4937ddb0f0512f6c247ba2856af27c4d812e5218a3fcc28' 
  AND token = 'Rfc+zBkIHNhXtYpjOVUfloR+k/C4zummEtl6rglLNgo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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