SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a940afd1f617f77bb3cdd0c790eb387737cdd8a5b914287cb6b82501a8926f8' 
  AND token = 'AJepynlJkMnJS/JE4sfsLlZqs+9L2qmjg+gzV+sUFEs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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