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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '83a8f4d237fd799868672d1aed83a0db89c03f3db53aaf80555017b8c1e2538c' 
  AND token = 'ZWn8VCDDssJz5lCQFiHiqiR2ujkbzis9CPoRGlHebxA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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