SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '98f36cb5c134a00702947d6b5db9ff031fd3905a54831f1a1c6d98b968799c76' 
  AND token = 'LjvQ6xs/bTB0fJNI9wJsh7hPbMoxRPqGtkXynZh+3ZM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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