SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff51172bfa9d857175b48dcaf8b088970c2d4bf5e63a315336b268c2ccc7cf12' 
  AND token = 'BjdEWbtF0BCTcNfeCUDfalan4PXglWTTrWdD8OAsR8E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}