SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d400a16f497f45ba8bf461811924c260dc138422eae04fdc5cfe356f5759fba' 
  AND token = 'P+MOV2mcVTr/1aMpoiKpTZejcE417CEyEnhqIruqsqA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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