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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51ac1fd0e7e59408d5d05a5a4895565539394707dd39d95f8499f6a7ebd2177c' 
  AND token = 'hqJiFuFWEC55KVU7dTBYes9kefY5gReKl2dTazBT8Xo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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