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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3d5f80dab7dbcfe3d3ec097618c8d374a6be0dbc7c8e61e4690a9f9c565b6d1' 
  AND token = 'U+Y/fENOnhVSKyZe1h6Bn/M8RF9RtzdwWNucqMsaMUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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