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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '38c42bcb19f08bbc2c4658a9e7853157ef39a51930029017d5a03d37acf6f852' 
  AND token = 'CKScYb+bTgW5bHc0eqdNYbq8TwgzSHfqqz5kFfBm2OQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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