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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31b0f1febb35401897413b7897d7921f6b76bd3c2a0f1f191d3e916db6d367b0' 
  AND token = '5OekkR4z99ozEC19zcqABlbizEXs5X4N7dnK5/AzYv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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