SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '976985d298c34b797a027adc8d1f86e70d04478757aa4cb064db4c1a2f20cf3a' 
  AND token = 'lA9LH+82gx3Lt3h+XvllCnh5gyvNmbAmefLfsYz4qz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}