SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a763e7c3fa964f99f89637756434489bcd9a8b67d65af51c8da238ad2dc75fdd' 
  AND token = '7nEUoJ3cpWz/GhVZ6jpdX/niu6aoeAsOoJvQViHixtQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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