SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71d81bd9fb488e8e9721a495c776364fb51260ece743969c99549a2d83367c18' 
  AND token = 'kxsFyNqLP/B6VlSNLpb+VSbvw9jO2HRulJ3eZA2lGWI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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