SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe973071ad766663ecd307c36d269e2d1d4226c87e6fb1f6b45c2b010b251afb' 
  AND token = 'XXRleU+huAbQrutt1+NRT7hkaP2qLslbWFfjPigNhMY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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