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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81d5f2d7c8689abe8ec0f3d8588cbb53106bde2a371ba18e75a878bd6b1539bd' 
  AND token = 'ZXRh5lwA/WBzc1xvqSJMkNsrEeTNEsKHxvtIH8Q0nLg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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