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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e5e761f2193841fc7d1a7d6f5fdf33dcd835a7ed1ba1dddf92028caa3b87bb40' 
  AND token = 'U41MoVkHwLuVsfZKw1IZGHMJc0EyRbcBo2EhFtpC/fI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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