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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e3a9ccef446a6cf4945f43fdef2019db6791769ba7496b94c4bb7928cc89e459' 
  AND token = 'VKCx9XAqU1Sjv+YyI/NfmZ0s2HsYD0E4eD1j57YIG0I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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