SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad8f50a1ed2989dbeaa95af8107a7903d1e9431db7c668e672bd9429d9f58b90' 
  AND token = '5qtcIMwHqTYAt6pSP4Wc4vA1qhKSEFR1yL4AXOuhVRc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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