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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '257c3500d4761df14c56adfe255bcf8e2a2a94bde913bacb85ff5faf3e35b7bb' 
  AND token = 'KVNubMUuiaAdn0PZmmK3jlvz1nVg0EoQV7SQgdmXLvA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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