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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '03f6dd0b0df41cd8cf87f2cdb24fd493948a03c5c1a55e87d240ca9e801e2f4f' 
  AND token = 'f+UBgKLrFrTGfZ6KynqPWEcSyvrdhlTMkBtZC/Wgg14=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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