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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68b0bd9ffbd9e99845b806eed04e6fbfc0ae59a7421d560c7954536929bac1ac' 
  AND token = '2wvAEVMKzzvd9VJBYDGEaE2WJ8T2iNlnQUiIm/oERBk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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