SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '855f2cf57a0e54849463761ab592fad815efe5772951161a1c5758acf1ba2c13' 
  AND token = 'jzrdCZchG9KGcAifCVQYVtcDRzxKWYBm54/B0ECwIG4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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