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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7f3d17290b4b0e75faa60b75dbdf89e2312c49e2fcfdc07f8f7fa92330b06e5' 
  AND token = 'xLHpn+0gvBtn/lNJgsb93gIqmyqfMl6oxPY9FZMHges=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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