SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a7fc137eee546f28fcf3dbe728ead959bf37a914744bc33f8d923d1592c8161' 
  AND token = 'I+tz+l79ta/EXzkzg9wz/ei2+M6n80sidkijmSs4BvY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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