SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0321a6c7647dc9328a11d575694805bae6a8514ce0be21c2f9a18f8d6b615fcd' 
  AND token = 'l35jJ9ohcwGyIKpElqmkMNt+hcnG6lNKasQekzPsCMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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