SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3e578a29e3f541c158d93912e115f8f2437d2b8d7150eab836de67876532ff7' 
  AND token = 'hpve+QB2PXYiriKQ9n1wzyej9Y9OMiU+yqiVApKerYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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