SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83df5008ce364aa56be1077dc5a8df81ef115e15455c00f605ed77fb560ac1f4' 
  AND token = 'TRVJvQJtTBXwoACIQ1gAW+MDnYAIeOckzvAJpMy43Qg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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