SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b921f6df26a4a7e3b5a2c95d555bfe53f40be9e743ed1c87740cd5020bd1e1b8' 
  AND token = 'zx9iXMPXFpXmPnlYTWNtCx+0CxEo1/u0LkCAglGmMso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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