SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d196f4823aeee18e019c7c1f7f1567c39cd3fe0de81209ecc4f21399f0cd84b' 
  AND token = '6R8dKzmdZNSUZvxztiTg/uszhJ7+VHGuLWDrrsmKEoA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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