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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21ef682bc8131707bd8764ab90f6e65717b1ab9cb651079cb42be7b4e2f113bd' 
  AND token = 'MsmAJAtbNL/dLtwwbZhQYBl6BModFLE9jhv6/Jznh/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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