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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9a46b671b2b2e43121a6ba1886f16fa092ff7fa58f7e4dcac7cd24e31cb7f60' 
  AND token = '6gNHRwHSyoBqjXxJ3pnuQkcH+xsUzaTa7kGQlJF/pT4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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