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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'bf5c35f9c6ebb4d7ff47690e67f4aba00b76d3f031790e3114b3c46f22cc9feb' 
  AND token = '5d2YDc88FKjcXb2jQ654At4j9GdWpBmUVB+Vxw/oSuc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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