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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75d1bdb48b3fb1e517dd9ee10d7b73e590a5d70be1e823f0dd7e5fba982b39ce' 
  AND token = '3JZMNp/brtsZh79zM4bl7Ix1RtD7b5ljFRxJ55n9FCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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