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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '9c7f99369f21009602726d5b4b6e5269d61e7bad503dff0dd9afd1c0cf4f0fb6' 
  AND token = 'vQHUaundwzPzdekZISkvQ3pN+3eMDD4irOL/DFqbKjQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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