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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ddc29b1ce8e91e9f1f0af2bd01ef4e139f2e467d510a9c870da60ad242c0e46a' 
  AND token = 'PWCLxMe6gPiv1wKThssRZehHeCxPGE+UP8Fsp6q4tUE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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