SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56966455ecafd8a734af0746f0cf340fa84b4303f5826a5daa79e6fe8257ef62' 
  AND token = 'ufDOjXJ2q/VGN5R81vT7XLCQ0JROvAHNs+MTa+zKUqY=' 
  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"
    }
  }
}