SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b57ac60acf0b7d43588a1390c838eeae68ffd30f213fd14cf6f3f984000f324' 
  AND token = 'LEmcfPOixN8IXvhA7dV2JdiWbVTU6x5n7miyTmGFHlo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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