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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6cd59c200bbbb949ff8ddf7f8abe689f0a3d2a8d007e4166c7d2c01217b57df' 
  AND token = 'Nqt0D8SzSZs4lUYTr3fGreZNPSau4kdSpUyan7659aQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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