SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a4f7baa6269eecad1e5b8b4c8db9e8b13b6a4fcaeb873f4a1db982bcee73cad' 
  AND token = 'kK4wli2/RJrQVjvvGXhD6s4f/nYqrLT11is+flCKVFY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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