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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cf33c2a027831a6dcc3552eb8810882b8ab2001b29e2e2d3300aec9d214159d' 
  AND token = 'kMZPwiO7Pk4sJjFY6NVJBuP7ibsSnUmg9jPSVbxFU7o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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