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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b120a78cef318002d9ba56f21cef3f4a21f4a7dde5d87e3c9f5b292fc907c859' 
  AND token = 'SPd+VRGWrPfj48cddsEBtuAcx9qRPwgCpH1AqBlGcsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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