SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6bac20e2ad408335d268e09fd647d95e1b70b1d27d9822b9bcf8f3ed53745dd2' 
  AND token = '0UOvFzM8aLrRZcFG/ADQCeCKA0aXUKRXpUZM77iFVy4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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