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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b1fd8f9a3304b0eb1fe2bebe8a49a02c751243113cd7ada0c1e4c2964d7011a' 
  AND token = 'p2VrFHPtgcl4dd6SjQ4ruMuhLhGZpBEsHTFSdH/UVqU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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