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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8b19c5241f5b29d0aa18db19db4251f1ab4c78df0b79e76da54b62eb9a91f51' 
  AND token = 'DiobVf13AxFFFLmosqaiV1veAhOqZUywtHVwzjsK7HA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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