SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1768f11d54bedeedb5381de99b30b9df03569ca7a05a355cc91db4b658eda6c' 
  AND token = '91tKQQzFZyjyVPMNbxBdsxLRMxbARzEJ6GP9BfMlk+0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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