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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '304c38d96d6b4d29921e378f3ce6db2aa3e9a5fcfe37d97ff268325c3344648f' 
  AND token = 'KywQXoJnoZzIkBcns/brPTpsIFrPAZh+d2SBEoyxiy8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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