SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51553ef44b4023811f4b22dc4fd331f5ec9251d349216fcff8a1960bc2c5b35a' 
  AND token = 'DM/Lyr7vKqq2otPN0XS52mHFjdTJI+gmx7vYrJFYXEQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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