SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e81f6d1dfc9d3ee629912e7dc2cd41f6a92e385b1e061204e59418e2039e9745' 
  AND token = '4PTqIQ0OZXSbVtCJH8TLLaaUUzn8JzxcB9+B40LnSKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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