SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5551090b315a0c455175dccaddcfe598c780297094fcf6782594b586a310660c' 
  AND token = 'o55XSmlZsP/OFVBOVPghqqo1HcggtvkUN0p9EblzQz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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