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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3bc21f721abb1e4d4cd98cf7f13d77b84ee64e25d5df0fd802b384d4571346a' 
  AND token = 'vyTIvrhlICPjpuiTtMkczLnmY/5fM79mI5WjYMtnUtc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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