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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6de8c6dc012ce3615b5c21204fd9c9ee2def06099ebcfa1799e7689497d68ac6' 
  AND token = 'L34k90d57omIwcP5NoOT+VoXq1pkPcHPtHsxyOyaAjY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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