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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8103b7bc0a2fcc4fc12216e8e476c7ac4448755cbb76c7aa2bdf07f5f60a564' 
  AND token = 'K2OF7Fqo6I49dZ9Zfgj8Wks/BPkuuXXRj2A9APXPfmw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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