SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '420c940d82c5b25d2e233027e804249b1ab0aea15843e1a98c76bdccfa903a29' 
  AND token = 'Qtn+s/sCCzQCzixOueKDFpMRRGvl2puJfkAIY5Haf/A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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