SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cef20639b9d809bf1a10d04f9d6039a06840861ec06faf95dc49409e9affa526' 
  AND token = 'myYfBMx+ivGWynZHNHomYNhoeTcloWwGggKi5R/aPOU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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