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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4e8538c0790a9dc58666fe022ee8a581e2b5f067c12118080739a688aba98f62' 
  AND token = '56T/pWF650GWGip8w6lzlvXfC93T0QN9E2dNhqDv0ok=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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