SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af7a1f198f28f8ed94e1bb31de8d02d283cd2912db86cfd1521716d76e36a516' 
  AND token = '/JJQqvVgDLqJdkA2Dgj4f40zMFZuGnOAiXic03YEyWQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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